Worst Credit Provider which gives credit and expects 25 to 50% payment back on monthly basis

This credit provider is the worst every, they call you everyday for payment even if your payments are on time.. They will send you 3 different sms's a day with 3 different amounts to pay.. I have been emailing them several times to obtain clarity on how their installment is calculated and never received an adequate response.received a statement today reflecting the months installment and the payment over due but the minimum payment due is more than these two amounts put together. I have asked 3 times for a settlement statement and called in telling them I will settle the account in December when I get paid.. I admit I have missed months and that is due to their harassment I rather js settle it one time and have it closed..they are now harassing me at my work place for an installment which is 50% of my outstanding balance.. I have not even used the account since Feb as my card has been ******.. Their staff are ridiculous, when asked if we can set an arrangement for ths month they said it's not possible.