iStore old number

On the 28th of April I went to iStore in Eastgate to buy a new iPhone 15pro and contract. They were busy with me for about 3 hours and when I came home, I found a new sim with a new number that I didn't want. I wanted my old number but the sales lady just wanted to make a sale and didn't explain to me that she can not do a new contract on my old phone number. She never asked me if I wanted the contract on my old number. She just went ahead and did the phone sale and contract with a new number.