Two different accounts in one house

The internet here [Edited: "Language"] and I want to pay for my own separate modem and router I’ve already tried the boosters and the extenders and they do nothing. I don’t understand why USPS would be a problem in having two different accounts when the names and account numbers are different. And when I decide to move I still have to call and verify my account with the name and number to cancel it so why can’t I have two different accounts in the same house.