Just because a person says they have 36 years of flying experience does not mean that they fly all the time. It just means that he has flown during the last 36 years. Perhaps the original seats were all the TA could get at the time of booking. Maybe the OP does not know about OLCI.

He experienced bad service and he is telling us about it. There are ways of a CSR to say things and ways NOT to say things. I personally would have not aggravated myself and waited to get onboard to swtich with someone.