In my experience it doesn't make much difference whether you pay the bills or not.
They sent me to a debt collector more than a year after I had closed my account, for something I didn't owe them (it was a bill for services after I had closed my account and been physically disconnected). When I tried to talk to them about it, one of their call centre managers eventually admitted to me that there was no public number that could get me through to a call centre that had anyone able to sort it, or anyone they could transfer me to who could sort it, so I might as well stop trying and sue them.
I got it sorted by tracking down one of the company executives home contact information and calling him about it. I harrassed him considerably less than the debt collectors harrassed me.
They sent me to a debt collector more than a year after I had closed my account, for something I didn't owe them (it was a bill for services after I had closed my account and been physically disconnected). When I tried to talk to them about it, one of their call centre managers eventually admitted to me that there was no public number that could get me through to a call centre that had anyone able to sort it, or anyone they could transfer me to who could sort it, so I might as well stop trying and sue them.
I got it sorted by tracking down one of the company executives home contact information and calling him about it. I harrassed him considerably less than the debt collectors harrassed me.