Calculating monthly payments please help

Debt_buster

Hi Im not sure if this is the right place to ask. 

I have some catalogue accounts but they have not been very helpful when I have asked them. Some of the items on the accounts were purchased by a family member, I have been trying to work out their monthly payments with the interest added, but Im finding it very difficult. 
How do I do this? Is there a calculator that will help me with this? 

[Deleted User]

Your credit agreement will tell you how minimum payments are calculated. 

If you want to pay more than that, then you can and less interest will be applied as a result. 

But you'll need to know how much they owe, how much they intend to repay, over what period and what interest rate will be applied.