Maybe an acknowledgement that is a limitation that they understand and it would be something they could change in the future. Maybe showing understanding that it is surprising that a credit based system goes into negative.
I don't know, this was not the first time I got surprised by their system.
Before that I preloaded my account for a couple of credits (+vat). Then they switched to monthly invoicing (+vat for my existing credit). Basically I got double VATed (?) for the single initial payment. Paid for 12 months upfront only to have to recharge more quickly. Why should it be my problem that they have problems understanding billing and building billing systems?
In the past when I signed up it was advertised as usage based billing with the fixed monthly fee somewhere in the fine print? But there is also some usage minimum because at some point I started getting credits used. But not in the first few months where my traffic was under some threshold.
It doesn't help that they constantly move things around in their website with no clear thought. Like how I was corrected in another comment thread with information that isn't on the expected pages like pricing or terms of service.
Maybe they just lack understanding of user experience. Or I'm just a dumb user. I accept either theory.
edit: honestly I don't know if I was double VAT situation or just became a non VAT except company, and ain't gonna dig that up, but if it's the later they should have swallowed the cost for existing credit because changing expected outcomes mid way is no bueno.