I sent back merchandise purchased on a credit card within a short period of time after the purchase, as it did not suit me, etc. & requested the proper credit back for the item.
The credit card company issued a "merchandise" credit, however, the credit card kept the full amount of the item on my credit card! Within a short amount of time, they started to bill me with interest. I disputed the amount several times. They actually notified the credit agencies and added it to my credit report dropping my score tremendously! I notified Experian via letter/certified mail.