It is possible that you are paying the correct amount – the first month or two is often charged at a different amount to bring billing cycles into sync, but you need to ask Three to be sure.
At the moment the best way to get in touch with Three is the chat box on the three website – it puts you in touch with a real person from one of their stores (working from home), and so far we have always had a quick response. Full details here: http://www.three.co.uk/three-store-now.
Generally switching to a new contract is more efficient than using Add-ons for an extended period, but during Corona Virus isolation cost isn’t the only consideration so an Add-on or Bolt-on could be a good alternative.
A 30 day 6GB data boost costs £8, so increased data for 3 months would cost you £24. A fresh contract or upgrade could be better value, but for the difference of just a few pounds over 3 months you should choose whatever you are most comfortable with.
Bolt-ons use recurring billing so you would need to remember to cancel when you didn’t need it any more.
If you are trying to secure access for an elderly or vulnerable relative then it is ok to think outside the box. Connecting via wi-fi is free, so if any neighbours have a good broadband connection and the wi-fi signal extends far enough they may be willing to share the password on a temporary basis.
You cannot transfer a number from one Three monhtly contract to another unless it is a specific “upgrade” contract.
It is really important to undertand that if you order a brand new Three contract then you will be unable to transfer your Three phone number to it – either now or later.
Your contract won’t automatically after 2 years – you will continue to be billed monthly until you specifically ask Three to change or cancel it.