Why is my direct debit set higher than I have been paying with my previous supplier when the rates are lower ???

DDs are normally set using the previous years usage information for the year and divided by 12 to give a monthly payment.

@hu8aberg1_ @Scudo is right. The Direct Debit is set at your quote amount, which is based on the annual usage figures if you provided them, or an estimate for your annual usage if you did not. If you think the payment amount is incorrect you can change it here: https://account.bulb.co.uk/dashboard/payments-and-statements/payment-settings