STOR-AGE DEPOSIT NOT RETURNED

Please explain to me how you can keep a deposit for 14 to 21 days, without returning the interest? I rented a 3x3 unit for 10 days. I removed my goods on the 13th of November at 4,40pm. Check your cameras. The removal truck came at 4,30 in the afternoon. On the Monday , I went to return the grey disk and was told, Oh no you bought that, it is now yours and if you ever want to rent storage units again, we reactivate it. I didnt know that I had purchased it, I thought you returned it along side getting your deposit back. More fool me. After many call, still waiting from yesterday afternoon 2pm for the accounts department to call me back in a half hour, as their lines are very busy. Oh it must be because the financial director , who releases the payments decided to take a long weekend so no one could release it. Or is it because of covid? Horrible service, we apologize , we are short staffed, covid, It might not be a lot of money, but it is my money , not yours! You receive the interest and dont even give that back. Imagine all the interest accrued on the deposits and the rest. If I rent a car, I get the deposit back straight away. If I rent a trailer or tool , I get the deposit back straight away. Not you guys. What a great business model. Kudus for that , but jeez surely the quick rentals are the ones you should be looking after.