Vibrating after tire change?

They took the A/S tires off in November and they were fine. I went in April to get winter tires off and leave and there was a slight vibration but attributed it to the road that I was on. I got home and it was still doing it. The next morning when I left for work it was worse and lasted the whole 17 minutes ride to work and has been progressively worse. I took it back the first day and they couldn't find anything wrong, so I left. 3 days later it was way worse and once I hit 45 it started to shake, and I couldn't even drive to 50 to go on the highway it was so bad. So, I brought it back again and they found a "broken belt" on the driver's back tire. So they told me I would have to buy a whole set of tires because you can't mix and match them and they don't make the brand that's on there anymore (tires were on the car a year ago when I bought it) so I ordered Michelins a/s well 2 weeks later they came in the manager calls me and I told him the story and said I did not feel like I should pay for the tire because it was all fine when they put it in storage. So, something must have happened to it there. So, after 4 hours of waiting for him to call me back he says I will pay for the one tire just to be "the good guys" (I suppose) and also, he says oh I found the tire that matches (miraculous?) So okay I change one tire and leave and you guessed it still doing but like last time not really bad and then got progressively worse. 4th time I wring it in yesterday and he calls me last night and says well umm we had to do a forced balance on it so the charge is $278 and I said why am I being charged for something that is not my fault. He says not our fault either. So what do you think?

I think he forgot to balance that last tire he put on.

Hi Joe, well, I went and picked it up and paid "under protest" and he kept insisting that if it wasn't done now, it would have been done and I would have had to pay at the time they changed my winter tires in April. I said, "Well wouldn't that have been a lot better than me having to come here 4 wonderful times with my high anxiety and the cost to take time from my job to sit here for 2.5 hours each time before you even brought inside. I am not happy about this! I told him this. So, he tries to console me or pacify me by saying that they took off the balance cost for when they changed the tires. I said "Well, you said includes balancing and the air thingies with the price of the tires". So, he took $178.00 off for that original balance and still charged me $278.00 for the forced one. OMG, I don't know what to do here.

Also, what can I do about this now that I have already paid for it? I suppose I scr**ed myself I think. And how much was the orifical price for a forced balance? Wowzer looks like $456.00 Holey Moley and this is at the GM dealer service department, not cool.