Charged for both 4G and 5G

I was supposed to cancel my 4G data. I spoke to Zahir and he convinced me to upgrade to 5G at no extra cost. The 4G was supposed to be cancelled as soon as the 5G was activated, and I was supposed to be charged pro-rata for the 4G. However I was charged in full for the 4G even after I started using the 5G. This was all confirmed on email. I should be credited for the 4G from 27-30 April.