Yeah, miles. It very well may have needed replacement, esp if your chain was overdue. The cassette will "mate" the the chain; it's not uncommon for it to need replacement at the same time as the chain. I usually replace each once a year (chain twice, usually).

However, they should have told you that they were switching the 25 for a 23. They most definitely need to know about that "mistake". It may very well be that the 12-25 cassettes are hard to get in stock (that was certainly the case last year with the 12-27 cassettes, which is what I ride).

MP, you have a 29??? (I'm jealous!) Which rear derailleur do you have? Are you on a double?