I’m in 20 bundle

[Tony11]

I’m on £20 pay as you go and get 40 gb but u do 50 gb for same price I’d like to get 50gb for what I’m paying now can I get a call from you please 

[Enlli]

All customers here so we can't do anything account wise. Also, O2 don't do outgoing calls, you will need to contact them

Customer Service Number Charges

From your O2 mobile 4445 Free

From a landline 0344 8090222 Standard UK rate

From abroad +44 7860 980 202 Free†

[Oxonian]

So you @Tony11 are currently on the £20.00 Big Bundle :-

Big Bundles: Eveything you need to know – Help and Support | O2

https://www.o2.co.uk/help/pay-as-you-go/big-bundles

And you want to go onto the £20.00 per month Rolling Plan :-

Rolling plans | Help and Support | O2

https://www.o2.co.uk/help/pay-as-you-go/rolling-plans

The latter page also says :-

If you're already an O2 Pay As You Go customer you can switch to a Rolling plan, and keep your existing sim and phone number, by logging onto My O2.

Do take note of the section headed "Paying for your Rolling plan" as :-

Rolling plans let you set up a credit or debit card payment that automatically buys your allowances each month....