How does recharge/payments api work?

[Aravs7]

I see lot of websites popping up which offer an API which can be used to recharge mobile credit or pay dth/post paid bills. How do these APIs work? Do they interface with other web services which merchants expose? Do billers like Airtel have an exposed API which these companies use?

 

[iChaitanya]

Do billers like Airtel have an exposed API which these companies use?

Yes, I think so. Experts can shed some more light on this.

 

[avi]

Yes. They have an API, but it's not public and you will need license to use. You need to be a registered company and have some XXXX amount invested/worth of company.