Enquire regarding a new service with correct dates

Not too long ago, I had unlimited data with router, and 2 sim cards for two phones with Rain... I eventually had to cancel because it was impossible to change the invoice date from the 25th to the 1st. Then eventually they suspended my services, three times, even though I was paid up. Anyway, long story short. I want to get the unlimited data router - month to month, but I want to know if will be possible and to be invoiced permenently for the 1st of the month, so to pay(have the debit order go off on the 1st of each month. I am writing here as on other sites one never receives any replies. Please advise as soon as possible, so I can go to a different provider if you can't do this