THE TELEPHONE is, by nature, a rude instrument. It has been encouraged to believe that it has the right to barge in anywhere at anytime with its shrill summons, and expect people to drop whatever they are doing to attend to its demands.

Being always in such company, as it were, is the only explanation Miss Manners can imagine for the high standard of rudeness she has encountered on the part of the telephone company. She does not claim that rudeness is practiced by everyone there, nor that it is unique to the telephone company, but she does find it there with unacceptable frequency.

Take the matter of placing a simple call that requires the services of an operator. (Many that previously did are now handled automatically by a machine that, Miss Manners noticed with gratified surprise, actually says "Thank you" to the dialer. You are welcome, little machine.) MANNERS, From K1

"This is Catherine Sherwood," says the caller. "I'd like to make a collect call to Sterling Wallingford."

You would suppose that the easiest thing for the operator to say next would be, "I have a collect call for Sterling Wallingford from Catherine Sherwood." Not likely. In Miss Manners' experience, this coincidence occurs in perhaps one out of a dozen calls. In one or two other instances, the operator will say, "I have a collect call to Catherine Sherwood from Sterling Wallingford" or "from Catherine Sterling to Sherwood Wallingford" or some other interesting variation--but these are at least not errors of etiquette, so Miss Manners isn't counting them.

Most of the time, nowadays, it is "I have Catherine here" or "Cathy, calling Sterling" or "Wally" or whatever the operator decides to nickname them. Another possibility is "I have a Catherine Sherwood," which implies that another dozen of them are lurking by the telephone, or "She says her name is Catherine Sherwood," which implies that it isn't.

Miss Manners tries to be charitable and treat this as ignorance of the rule, which is: Accept people's names exactly as they gave them to you, neither taking friendly liberties nor expressing doubts.

But let us put the operators on hold, and switch to the service department, with which Miss Manners had the misfortune to deal recently. On one transaction, she made 72 telephone calls to the business office during a period of three weeks, on each of which she was put on hold for a period of from 10 to 35 minutes, to then be told that the person to whom she was talking was not responsible for that jurisdiction and didn't know or care to find out who was.

It is not Miss Manners' place to be critical of the business aspects of this. On the contrary, she can understand that with this method, the employes must be terribly overworked, and many of the people with whom they must talk are probably quite testy with them.

But she does think it basic courtesy to be considerate of the time of others and to show some corporate responsibility and sympathy for their difficulties. The employe is, after all, a company representative to the public, and it is rude to retreat into being an individual disassociating himself from the business at hand. And just because the company invented the hold button, it needn't use it as a weapon.

An occasional "thank you," even if strictly unwarranted and not from the heart, would help, too. Miss Manners would guess that the people might be willing to concede a contest of efficiency to the machines, but it would be sad to think that automation had also won out in a comparison of civilized behavior. MISS MANNERS RESPONDS

Q. I have been living for the last three months with my boyfriend, and my sister (two years older) has invited herself to visit next month. In our past get-togethers, my sister seemed quite happy chatting exclusively to and teasing my boyfriend. She's very friendly and self-confident, whereas I am reserved and intimidated by her take-charge personality.

She has invited herself to visit several times in the past, and her plans fell through, fortunately. I am an unenthusiastic hostess to a slightly pushy sister.

Is there a tactful way to tell her she should wait for an invitation from me? I value her friendship, but I feel her ignoring my presence in the company of my boyfriend is a high price. Am I petty to create a possible rift with my sister over occasional flirtations?

A. It is possible that you are. Social instinct usually has one directing the charm, in such a situation, to the non-relative, on the grounds that the family accepts it on faith. But you know your sister better than Miss Manners does (you can hardly know her less), and perhaps you know better which instinct is prompting her.

You needn't create a family rift, however. There is nothing wrong with saying, "Oh, dear, it's not convenient for us to have you just now," and then suggesting another time for a visit.

If it happens to be a time when your beau is otherwise occupied, or elsewhere, you can greet your sister warmly upon her arrival by saying, "I was so much looking forward to a cozy visit with you, so I fixed it so I would have you all to myself."

If her face falls, it will turn out--without your having created a rift--that you weren't being petty.

Q. Your article on etiquette for gays both amused me and angered me. I realize my amusement was a result of my closet homophobia, which allows "people who are also homosexuals" to be publicly insulted and laugh along with their persecutors.

My life partner and my best friend is a man. Even if "marriage" were legally obtainable between persons of the same sex, I seriously doubt the two of us would seek to obtain such legal recognition. Our relationship does not include sharing sex, and we both prefer it that way. But aside from that, we relate to a great extent as a married couple.

Therefore, I tend to assume that when I am invited anywhere and the invitation includes my "spouse," that it is within the bounds of etiquette to take my "friend" and inform the host that such is the case.

I personally feel that society has no concern with anyone's private life. At the same time, I feel I have the right to be as public about my "sexual affiliations" as heterosexual married couples. People who also happen to be homosexual desire our meaningful, supportive and loving relationships to be as recognized as those of people who also happen to be heterosexual.

If this is what you intended to express, I commend you for your humanity. If you intended differently, then I correct you.

A. Why did you feel obliged to explain to Miss Manners that your relationship does not include sharing sex? Did she ask you? If she invited you to dinner, do you suppose she would demand to know what you are likely to do before you leave home or after you return?

The fact is that there is altogether too much recognition being demanded nowadays concerning people's private lives. Miss Manners makes no distinction here between unmarried heterosexual and homosexual couples--indeed, how could she, as she does not inquire into people's personal preferences when she sees them socially, unless it is to ask whether they are allergic to shellfish.

Nor does she approve of guests "informing" their hosts whom they will bring. Many happily married couples no longer go about socially in tandem, while many varieties of other couples do. Pity the poor host, who is only trying to be hospitable.

It is a general courtesy to invite married couples together socially, for evening or weekend parties, although it is not necessary at weekday lunchtime. In former times, they refused unless both could attend, but now one can accept without the other.

It is also courteous to invite two people together who are known to be a couple socially, regardless of the composition of the couple. The trouble is that the hosts may not know--in which case, you can say to them, "Do you mind if I bring Adam? We generally go about together."

Miss Manners assures you that she would make no distinction in this matter between this and your saying, "Do you mind if I bring Eve?" But if any of you used the occasion to demand recognition of your intimacy, you would not be likely to be invited back to her table.

Feeling incorrect? Address your etiquette questions (in black or blue-black ink on white writing paper) to Miss Manners, in care of this newspaper.

Copyright (c) 1983, United Feature Syndicate Inc.