
we live in different countries so I am not sure not prepaid system is running in there, so sorry I cannot help you..
but in my country.... Our prepaid services is by loading system... We go usually to a sari sari store who offers load and pay what we can afford to buy and it is sent to us via sms and use the load by your preference..
A telecommunication company here now offers the load in our phones to be use as cash to buy items in google play. Which is pretty cool. No need for credit cards just my phone and load and if USD is hella expensive for you try Korean won... It is much cheaper... I will try that in some time soon

http://www.mangago.zone/home/album/30597/
This good person showed ways for us to buy chapters more cheaper
-_- I really need to get a debit card so I can start supporting the artist... But firt I'll need to get a job... Ahhhh high school struggles T^T