Xfinity mobile billing issue

A few months ago, I informed an Xfinity representative that I did not want to activate the Xfinity Mobile service. I have contacted three customer service representatives, and they all confirmed that the account was canceled and any balances would be waived. However, a few days ago, I received an email from Sequium Asset Solutions stating that I owe $56.02. I have never used the Xfinity Mobile service at all, so why do I still need to make a payment? Why am I still receiving a bill? Please help me look into this. Thank you.