remove multi sim

I went to 8ta centurion mall on 2015/03/09 to removed one of my multisim from my contract to prepaid. The agent who tried to help gave me a cancellation form. I asked if the form are correct and explained that I don't want to cancel my contract but only want to remove one of my multisim. He advised me to complete the form and put my instructions on the form. After completing the form I asked again if my contract won't be cancelled and if will keep my no. He told that my contract will be cancelled and I'll loss my no. I told him that's not what I want, 8ta should action my query as stated in the form. He said he won't guarantee that the instruction will be actioned as stated in form, 8ta will just cancel the contract. I asked him to explain why is that so, he said he was only joking about cancelling the contract but we don't guarantee that I'll keep my number and he left. I then asked the other agent to explain why he can't guarantee me that 8ta will action the request as stated in the form. While the other agent was explain, he come and told everyone not entertain me and if I don't want to take his answer I should just take my form to another store. He said i can repot he to 8ta