You want to create your own wallet or use any existing wallet as a payment method. Creating a Java wallet with a 5-6 developer within 2-3 years will help you come up with a fairly competitive product if the goal, design and process are clearly defined.
If you are looking for existing providers, you can use the Paytm wallet, which offers an SDK for Android / iOs along with several other server-side mobile utilities. You can research them on the PaywithPaytm website.
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