Thanks for getting in touch.
I'm sorry to hear that you're experiencing wifi issues and that the payment schedule on your account is causing problems.
Have you had the opportunity to run through our wifi troubleshooting guides here?
In terms of the payment date - you're right that we can't change this. It isn't necessarily a refusal to change the date, more that we simply don't have the facility to do so (yet). In the interim, you can make manual payments via debit card through either the member centre or one of my colleagues in the Customer Services team (0800 328 4620) up to 14 days after your payment date. Although you'll still get a reminder that the payment is due, this can be dismissed through any Windows based PC/laptop and you'll then be able to browse without interruption.
Let us know if there's anything else that you need.