Is it a good thing to upgrade my contract earlier than the expected upgrade date?

Hi there everyone Can anyone please tell me if it's a good thing to upgrade my Telkom mobile contract earlier than the expected upgrade date? I am due to upgrade my current contract (which is a smart plan 100 for an iPhone 5C @ R258 a month) on the 26th of September 2016 but Telkom mobile has informed me that I can upgrade earlier on the 26th of June 2016. I just want to know from anyone who has had a similar experience in upgrading their contract earlier with Telkom Mobile if it's ok to do so as I have read posts on Hello Peter a while back where people have upgraded their contracts earlier and money was still being debited from their accounts for their old contract as well as for the new contract. I did ask a guy at the Telkom store in Baywest Mall in Port Elizabeth what the procedures would be if I upgraded even earlier than the 26th of June 2016 and he told me that I still owe R1050 on my current contract and that will be added onto which ever new plan I decide to go onto until the total the total amount on my current contract is paid in full thereafter I will only pay the amount of the new contract. I am going to wait until the 26th of June 2016 to renew my current contract which means I won't owe them the R1050 anymore on my current contract will this be ok or do you think they will still debit my account? Thanks