I believe it is against the merchant agreement to withhold service after a valid charge-back. That would be a major and unwarranted retaliation, which you could probably sue and win a large class action if this is really happening.
I will say, I should have made more clear, the first step in a dispute will be to contact the merchant. They will have a fixed number of days to reply and correct the problem.
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Apologies if you knew this already.
Losing my Steam account due to a chargeback is something that never occurred to me. It's a chilling thought!
Same thing can happen with any account, of course, but Google users tend to have a larger number of more important eggs in a single basket....
Perhaps worth adding, I was/am 99% sure how the charge occurred, and that it was a Heisenbug from when I'd trialled Prime. So there was no question of punishing them for being a bad vendor, I just needed them to bounce the issue around until it landed on someone who could fix it (which is essentially what happened).
I think the real root cause of situations like this is that social teams sometimes have more/better options for escalating issues than customer support does.