Omega Geneve ST3660832 (1981)

It's not clear to me whether your "authorised agent" repaired the watch locally or shipped it to Omega Switzerland for the initial service. In either case, the timekeeping is unacceptable after an outlay of Omega-type money for repairs.

My suggestion would be to take this up directly with Omega Switzerland. First step should be an e-mail to Customer Service through the Omega.ch website. Be sure to enclose scanned copies of the paperwork you received from your agent, any invoices from Omega and other correspondence.

If there is no response within a week, then follow up with a telephone call to Bienne.

Other that the above, don't know what else to tell you,
gatorcpa

Just to follow up GatorCPA's reply, if you have a look at this thread:

http://omegaforums.net/threads/european-jewellers-fraud.89/

Where another member had similar difficulties with getting his watch serviced, as soon as he contacted Omega directly, rather than just the dealer, they went to rather great lengths to rectify the situation and solve the problem to the member's satisfaction. Omega is really putting a great deal of effort into their reputation and brand at the moment and if you let them know about this directly I have no doubt they will step up to the plate.