bill problems and others

I have internet service through Xfinity, as well as mobile phone service for two lines. For the past couple of years, I have been paying my Xfinity internet bill using my UHCard. This month (October), my statement—which usually appears around the 7th—did not show up on time. I spoke with customer service, and they were able to locate the statement and send me a link to view it (though it still did not appear in my account). Once I saw it, I made the payment on October 10th. A few days later, I received a message from Xfinity Assistant stating: "Your Xfinity payment is overdue. Please pay now to avoid any applicable fees. Debt Collector Lic. #10316-99 Txt help or stop". I called customer service, and the representative said they couldn't find anything unusual; they urged me to sign up for automatic payments to receive a "financial benefit" and may be solve the problem—but why would I want automatic payments when I always pay the bill myself using my UHCard? Today, I went to an Xfinity store, and the agent checked my account and confirmed that everything was in order. When I asked how the message I received could have been sent, the agent said they didn't have an answer and suggested I try to figure it out myself—even though the problem clearly isn't on my end. I have never missed a payment; in fact, I usually pay my bill the very day after the statement is issued. How can Xfinity threaten something as serious as sending an account to collections without taking any prior steps to verify the situation? Could anyone shed some light on this troubling issue? Thanks in advance.