Accidentally made 2 premium payments, help me cancel

[SimayEsmek]

Yesterday, I tried to buy student discounted premium subscription. I tried 2 times to upload my document and on first one I had an error. So I assumed It did not work and tried second time, It worked. I waited for confirmation e-mail but I had an e-mail says it is rejected and I thought It did not work then I went through normal premium account page. Today, I had  an e-mail saying my student ID approved and payment completed. First e-mail was connected with my first attempt which gave error and today I have 2 charges on my account one is full payment of regular premium other is discounted student payment. 

I really don't want to pay 2 times per month, so can someone help me cancel my regular premium payment?