I changed user name, how do I change it back to what it was?
Once it's changed it's permanent; it can only be changed once. Sorry.
@fangg wrote: I changed user name, how do I change it back to what it was?
If an employee doesn't take care of this for you here, Comcast Security Assurance should be able to help. Give them a call at 1-888-565-4329 (from https://constantguard.xfinity.com/help/report-abuse/). Note that this is NOT one of the general customer service numbers.
The first-line reps there are sometimes not very helpful, so you may need to be persistent and keep at them until you get a satisfactory answer.