Hello,
I've seen there is BillToMobile option to charge RPs with your mobile phone. But it is only for USA and it's limited with 3 providers ONLY.
You should consider adding Boku payment. It has more countries (USA and Europe) and it is possible for almost every provider. I am using Boku myself to charge RP (riot points) in League of Legends. It's easier, not requiring ZIP codes like BillToMobile does.
Anyone else?