Harrasment as a cutomer of Mr Price

I opened a account at Mr Price. We pay a amount every month that we can afford. Mr Price phones up to 8 times a day to make a payment when you explain this is the amount you can afford to pay they are rude and want to forse you to pay more. They phone every day I have lost my temper I know I must pay every month I refuse to answer their calls. I refuse to be treated like a child. I know what my oligations are to pay my debt and I have reached a point were I am totally going to loose it this is harrasment!!! I have asked to make the instalments 12 mnths so that we can afford the instalments. They refuse to do it and now they charge you R70 a week more interest!!! This treatment as a cutomer is unacceptable!!!!!!