I recently returned an item as i couldnt return it...

I recently returned an item as i couldnt return it sooner but i thought that it was within the time limit i didnt know that the money would be reduced. I got a dashcamera as a gift for Christmas,the main button on the camera was faulty and we returned it i would of been happy to get another dashcamera but they didnt have any left.I recently returned it as i couldnt return it sooner but i thought that it was within the time limit i didnt know that the money would be reduced. I was offered an exchange of 3 it orignally cost 15 Very disappointed with the customer service and angry that they reduced the amount to 3 i never heard of that happen anywhere else and i have returned stuff to other shops and i was given a refund or credit note for the amount i bought the item for. It doesnt even deserve 1 star.