Recently I received a notification of automatic purchase of OpenAI credits. This surprised me because I didn't actively use their API anywhere for some time. Later, I realised that the old credits expired, which triggered automatic purchase of new credits, which I set up back when OpenAI models had the best quality / value ratio. Of course, I agreed with this, so that's on me (although at least a notification prior to the expiration would be fine, I would burn the tokens somewhere).

It seems Anthropic does the same. You may want to check your credit balances on these platforms if you switched to other providers, as I believe many people did during this last year.