@Leannej
Power cycle your router now (tech-speak for switching it off, waiting 2 minutes, and then switching it on again). Now your electricity is stable again, this gives the router a chance to come back to a settled state.
If this doesn’t fix it (and I’m not all that hopeful of this), then you will need to talk to the Now Broadband team.
Telephone numbers I have heard flying about for this are variously 0330 041 2518 and 0800 759 1213 but should anyway be in your documentation from Now.
Set a Payment PIN on your account so that no-one but you can buy memberships on it. Check your bank accounts monthly for any other unexpected payments to Now. That way you can at least nip them in the bud, while you and Now figure out whose fault they are.