incorrect bill

Have a contract SIM from your company and my bill is 8 pounds per month on contract and now today I have seen it's 33 pounds  which is unacceptable and when I got this package the data package was 50 GB now they decreased it to 30 GB and other thing is that bill should be 8 pounds and now  I can see my bill is 33 pounds which is unacceptable I can't pay more than what is in contract and also there should be a cap on usages and there is no option in your app to put a cap on your usage so please look into it I can't pay that much. Also correct my bill and recent me 8 pounds .