Welcome to Community!
I was able to find your account using your Community username.
I've gone ahead and checked your account details and can see that the change of your plan was done online last 15 April. TPG is a prepaid service, hence process begins as soon as we receive the specified funds from the customer.
As payment was done via direct debit, I can see that the payment is still in progress. It usually takes 3 to 4 working days to clear after your details have been entered into our system.
I hope this would clarify things. Nevertheless, should you need further assistance, please let us know.