STOP HARRASING ME WITH YOUR EMAILS AND SMS

just don't understand why is it so hard for Mr price to stick to the agreement. I have made a payment arrangement with them and even arrange a debit order for them to get their money on time, but they keep phoning me sending me emails demanding the payment with incorrect amount. I just don't understand how they operating. This is quite irritating and not acceptable. Please treat your customer with respect. I will appreciate if you can sort this out.