I have the same problem with my Defy phone. Although my home account is Comcast, my phone gets hijacked by local xfinity hotspots.
This won’t solve your problem if you are not a premium or higher level xfinity/comcast account holder.
Without an account you can be a guest for a total of 2 hours per month with no log in, but how do you control that if your access is hijacked?
If you have a household Comcast account of a premium level, you can add use your Comcast log-in and user name, same one as you would use to log in to pay your bill.
you can have up to 5 people added to that account with their own log in. It’s part of comcast service. It took a 38 minute phone call to xfinity tech- 855-308-9454. You will need to be authorized by the main account holder, and need that information, their phone number, name last 4 digits of ssi and their authorization, which xfinity accepted over the phone.
personally I don’t especially like this solution, because it forces you to use Xfinity weather you like it or not.
I think the new hotspots are stronger, and therefore my local account shows as not working, even though it’s up and running for computers.