You may recall that a few weeks ago I published a letter from a reader who has been receiving harassing telephone calls for several years.

The harassment has continued despite several changes in the reader's unpublished number, but the telephone company says it cannot trace the calls because they involve an obsolescent central office that is scheduled to be replaced soon.

William D. Erickson of Annandale comments: "I was being harassed by telephone in 1970. C&P said they couldn't stop it, but offered me a change to 'unlisted' at no charge.

"Later C&P went to Richmond and claimed (but never showed statistics) that unlisted phones cause lots of 'Information' calls. They charge $1.45 a month extra for unlisted.

"The Shenandoah Telephone Co. of Edinburg, Va., has a different approach. They list all subscribers. Those whose numbers are 'unlisted' are shown as 'Unlisted.' That helps everyone, at no extra charge. Isn't the Shenandoah Co. approach fairer to all?"

Let the record show that I may be prejudiced in this matter, but I will answer as best I can.

I cannot cope with the volume of telephone calls generated by my job, even though my home phone number is not published. Quite naturally, I think that people who need protection against day-and-night calls should be able to obtain it -- and to obtain it without being charged extra for not being listed in a directory. Although I have a high opinion of the Bell System and the people in it who provide us with the world's best telephone service, I am strongly opposed to the policy of charging subscribers extra for keeping their phone numbers out of directories. I think it is illogical, unreasonable and unfair.

It never occured to me that other telephone companies use the system described by District Liner Erickson, or that there is such a simple way to handle the problem. The Shenandoah plan seems quite sensible to me, and I commend it to Ma Bell.

I realize that it will not be a complete answer to the problem because I know a few people who don't even want their addresses known.

One is a loner with an unusual temperament, one is supposes to be paying alimony but doesn't, one is a businessman who frost manner does not invite prying questions.

I suppose that in a free country, one is entitled to dig a hole, jump in, and then pull the hole in after him if he wishes to -- and some people do.

They probably wouldn't want to be listed in a book that omits phone numbers on request but does publish every subscriber's address. To appease them, I suppose telephone companies would have to agree to omit listings completely for those who insist on it.

But I like the general idea of putting the public on notice that some people don't want their phone numbers known, so there's no use bothering "Information."

It has also been suggested that an appropriate symbol could be placed alongside the listings of people who do not wish to receive solicitation calls. For example, an asterisk could convey the message, "I pay for this service, you don't; so don't call me unless I have invited you to."

When the idea was first broached, the Bell System was noncommittal, and it was easy to understand why. A mountain of paper work (and therefore expense) would be involved in resetting the type for millions of listings. And when the new system was in place, there would be two mountains of work and expense in trying to police it.

Solicitors who work for telephone "boiler rooms" would continue to use sequential dialing devices that call every number in an exchange. Subscribers would continue to be annoyed. And telephone companies would find it difficult to preserve the integrity of the "no solicitation calls" symbol.

But surprisingly enough, Bell spokesmen now say the company is "not opposed to such an approach" to the problem. When subscribers are unhappy, Ma Bell is unhappy.

However, I think Bell managers are hoping that new electronic systems will solve problems of this kind quicker, better and cheaper. Not too far down the road, we will be introduced to systems that will do more for us, provide better controls, and perhaps keep the Bell System dominant for a while longer in what has become an increasingly competitive field.