Do service providers keep records of devices bought and activated on a customers account?

[Debiec68]

Tried getting a proof of purchase for a SAMSUNG J3 we bought at a BOOST MOBILE STORE. But was told they don't have that info.
But wouldn't they have access to past records of what device they provided service to?
Just want a list of ITEMS WE PURCHASED FROM THEM, AND HAD ACTIVATED BY THEM.
If this info is NOT available to the paying customers, I believe it SHOULD BE.
Service Providers should Provide Service. Right?!
Customer service - serve customer. Seems self explanatory.

 

[Sam_Gs7]

Definitely they should keep record of sales, that's why
is advisable to buy devices, from recognised networks
if you live in USA like Verizon: AT&T: T-Mobile,.etc.
Why when bought it didn't get an invoice..?