I recall getting something like that from a company using Sprint's logo, but the letterhead was printed in black and white instead of the normal colored logo Sprint uses.
They were warning me that my credit card had expired and if I didn't provide them with my new credit card number, my telephone service (they knew my account number) would be cut off. Only problem is, I have ALWAYS paid my phone bill by
CHECK after they send me a monthly statement in the mail. When I contacted Sprint, they gave some garbage about that company being the service that collects from the people who chose to have their phone bill automatically payed by CC.
IMO, Sprint gave account info to this company knowing full well that they were going to try to scam customers into changing their payment method to one that was more convenient for THEM. I threw the warning notice in the trash and continued to pay by check.