Billed twice for one month at contract upgrade

Whilst the upgrading of my contracts in store went seamlessly, Cell C has charged me twice for February 2018, one on the old contract subscription still, and then again but this time for part of the month the new contract.

I was under the impression that the new contracts will only take affect from the new month, thereby needing me to ever only pay for one month's subscription.

I would be nice if Cell C can rectify this, and once I see the error being rectified on my new statement, will I change my review to perhaps a 3. Because, in my opinion, the customer experience does not just include the direct client engagement, but also how the administration is handled at the end, such as the billing of the client.