Harassment of clients

These people are ruthless. I have had dealings with them since after lockdown. They phone continously. They start phoning at 06:45 every day, just on Sundays they rest. If I don't answer they phone my sister. Non-stop every day. I pay every month, I have even increased the amount I pay. They still phone. Every day the whole day. Why? And then when you ask them why are they phoning you for the 3rd time on the same day after you have paid, they say they are reminding you of the payment that is due the next month. Why? Am I paying every month yes, so why are they phoning non-stop. Then they drop the call. An hour later someone else calls. They are harassing me continuously on a daily basis and this needs to stop. My sister has asked them continuously to remove her number. They even sent a sms to apologize about contacting her and straight after they phoned again. I have blocked all their numbers, but they get new numbers every day. This is harassment and it needs to stop.