That’s true, it could work another way. But if you want it to work another way you’re going to have to become a customer of a different company. The monthly payment goes out every month regardless of the state of your account, that’s just how it is and what you agreed to when becoming a customer.
Because you’re most likely going to be using considerably more energy as we head into the winter months, and heating is required. The idea is to build up credit over the summer to help pay the large winter bills.
Remember, you’re in full control of your direct debit payment. You can set it to whatever you like. If £54 is too much then you could have just reduced it. There’s no reason at all why you needed to allow £300 of credit to build up.
Bulb can refund some of your credit. To do this you’ll need to follow the instructions for the process as detailed in the help section - just search for the word “refund” if you haven’t yet found it.
An alternative is to just change your direct debit amount down to the minimum £5 for a little while to allow your credit to be used up, and then increase it again to something reasonable.
Have you investigated why your meter readings aren’t being used? Are you submitting them at the right time, a couple of days before your statement is generated?