Former Rep. James W. Symington (D-Mo.), in the manner of a perfect gentleman and somewhat embarrassed, arrived at the General Services Administration yesterday, sat downand wrote a check for $1,870.22 to cover his unpaid congressional telephone bill.

Rep. Parren J. Mitchell (D-Md.), explaining that his $12,899.42 overdue phone bill is the product of a poor Baltimore constituency that calls him collect, announced he'll hold a fundraiser to pay it.

And Rep. John Y. McCollister (R-Neb.), sent a check for $468.75 to GSA to pay his bill.

In such ways, some present and former members of Congress reacted yesterday to GSA disclosures that 50 of them owed $64,726.89 on their Congressional phone bills.

But by day's end, the agency, somewhat red-faced itself, acknowledged it had erroneously included two it shouldn't have, Rep. John T. Myers (R-Ind.) In addititon, GSA revised the amount owed by former New York Democratic Rep. Bella Abzug from $2,838.13 to $1,217.69.

The charges arise from members' use of the Intercity Federal Telecommunications System. GSA collects fromthe Congress.

The office of Sen. Paul S. Sarbanes (D-Md.) said his $90.36 payment for phones was included in a $409 voucher sent to the finance office in Congress, which in turn sent payment to GSA. The agency hasn't realized the $90.36 was in the voucher, Sarbanes' office said.

Rep. Jack Kemp (R-N.Y.) said yesterday that $1,298 of his $1,441.16 delinquency was in the computer somewhere in GSA and that the remaining $143.16 is a matter of dispute between the finance office and GSA whether it's been paid.

One Senate aide saved her boss from being listed as a $120 delinquent at the last moment. Tipped off on Wednesday by a telephone company representative to the Senate that her senator was one of five senators on list being prepared by GSA, she quickly got a check to GSA that day.