Comment by intellectronica

Generally, all cloud providers have two ways of engaging with and billing customers. One is using a credit card, which is very easy for getting started. The other one is having an established relationship with a sales / account team and setting up billing by invoice. Smaller companies sometimes don't understand that and stick with credit card billing for too long. Once you move to production and have your own customers that you can't let down, you should really make the extra effort and move to invoice billing (with all the upfront overhead that entails).