The Utah Public Service Commission and US WEST Communications have worked out a rebate plan that will cost the telephone company $26 million, but save it at least $1 million.

On Sept. 22, the PSC ordered US WEST, formerly Mountain Bell, to reduce its rates by at least $27 million before Jan. 1, 1989, to repay its Utah customers for overcollections.But Monday, the three-member commission and the phone company signed a new deal. US WEST will cut its Utah rates by $16 million, retroactive to Sept. 22, and then by another $10 million effective Jan. 1.

The latest decision "eliminates legal questions that surfaced as a result of orders" by the PSC earlier this year, said W. Mack Lawrence, US WEST Utah chief executive officer.

The Sept. 22 reduction will result in a 6.2 percent cut in monthly phone bills, he said, or about $1.12 per month for the company's average residential customer in Salt Lake City.

And the $10 million rollback by Jan. 1 will translate into another 4 percent rate cut.