Do not care about loyal customers

I have been using Webafrica for a few years as an internet service provider, I have changed work last year in August (2023), and I now get paid on the 7th of the month. Webafrica refuses to change by debit order to the 7th of the month. This results in a declined debit order every month and a penalty fee that I must pay. All my other debit orders with other companies was changes with not even one complaint. Is it fair or even legal to refuse a customer that is willing to pay for a service, to change debit order dates.