Bad service / credit report

I had an contract with Cell C since 2007. I have only cancelled the contract in March this year because my wife’s phone was broken so we didn’t really use the benefits. I was never told if I don’t use the sim card my number will be deactivated. I found out my number was deactivated and I made an enquiry to keep the number last week the 23/10/2018 ( Tuesday ) I was told the number is still available and I must buy a sim card with 24 hours. I went to 2 stores that night and couldn’t get a sim card and it was already late to go to any other store. I asked if they can give me time until Monday ( 29/10/2018 ) and I will buy the sim card over the weekend. I bought the sim card over the weekend and Monday ( 29/10/2018 ) I was told that the number was given to somebody else because I didn’t buy it within 24 hours. In the first place did they blacklist me for that same number after I paid it in full and closed it in March and they didn’t remove it from my ITC until now which is also more than 24 hours. I feel like I am being treated unfairly because I had that number since 2007 and they couldn’t even give me a few more days to buy the sim because as I am working during the week. They knew I wanted the number back and they still went to give it to somebody else after I requested the number back. If they can so easily take the number from me who had it for 11 years why can’t they take it from somebody that only has it for a few days. I called that number yesterday the whole day and it was off so why can’t they just give me a sim swap on that number because nobody is using it PLEASE? I would like to get my number back even if I should take them to court for it and they should also clear my name.