Is my job of collecting credit card payments halal or haram?

I AM WORKING IN A CALL CENTRE IN MUMBAI , MY JOB REQUIRES TO CALL THE CLIENTS IN UK , WHO HAVE PURCHASED CREDIT CARD FROM OUR COMPANY ,WE HAVE TO COLLECT THE AMOUNT BY CALLING THEM ,AS THE CLIENTS DONT PAY THE AMOUNT BEFORE DUE DATE , SO THE COMPANY CHARGES THEM WITH INTERST ON THEIR CREDIT CARD ,SO WE HAVE TO CALL THE CUSTOMERS TO REMIND THEM ABOUT THE MONEY WHICH THEY OWE TO THE COMPANY .SO IS THIS JOB OF MINE HALAAL OR HARAM,PLZ REPLY QUICKLY