Delayed Payment letterafter

After years of trying to make monthly payments to edgars i finaly call and speak to a lady delrease gave me a settlement amount of R2241 and im told i was supposed to pay R2351 after. i paid the amount i was told to pay which in inclued the paid up letter amount. She gave a wrong ref number and i couldnt pay on the 20th nov and i had to go instore the following day to verify the ref . On momday i made the payment yet i get an sms i havnt payed when i called in im told they have recieved the payment but interest of 140 needs to be paid becoz i didnt pay on time. Whos fault is it that i didnt pay on the 20 th i spoke to louise and several other agent who say they will call me back regararding the matter. Im tired of calling im and ppl refering me to diffrent departments. I did my part with edgars and i cant keep running after them for my payed up letter. I also requested an ombus email and no one gave it to me. I need to provide this letter to edgars stores and the itc as per their process and my work needs payed up letters as to consider me as permanent employee. I payed up the amount. Ill find the ombus email myself sent them all the incorrect sms and all the telephone Recordings