How do I change from pre-payment to standard meters

Just moved into a house and for the first time in my 67 yrs am faced with a prepayment electric meter (key) and according to Bulb a top up gas meter. They have sent me a key and a top up gas card.

I am disabled and finding it difficult to use this system.

The electric meter is indeed a key type but the gas meter is standard .

I sent an email to Bulb requesting a change to standard meters and pay by direct debit which I have done for the past 12 months at my previous address with Bulb.

All I got was ‘there will be a charge for this’ and a phone number which is impossible to get a reply on.

Does anyone know what the charge is and how I can get something done about the meters - it appears Bulb just don’t want to know.

I am at my whits end at the moment.