I had the same problem with my car. The place that sold me the new tyres had two goes at balancing them, getting a little better the second time, and managed to lose one of my lock nuts. Gave me a few bullshit excuses and fairy tales for free though
Went some where else and paid again. Voila - perfect.
So my problem was lazy stupid pricks. Unfortunately they seem to be fairly common nowadays in a range of automotive "services".
That may not be your problem, but going somewhere else could be a good idea, particularly if your first place doesn't want to own the issue.
If nothing has changed except the tyres, and all was good before the change, it's a bit of a stretch to blame wheel alignment.