Go cashless in India (the cheapest and easiest way)

Don't have an expensive phone to use apps ? 
Also don't have a net banking account in your BANK ? 
Then NUUP is for you.
You only need :
 
1. A mobile phone
2. An ATM card 

NUUP (National Unified USSD Platform) is a mobile banking service provided by NPCI (National Payment Cooperation of India) which works on the USSD technology. Customers can avail of basic mobile banking services of IDBI Bank just by dialing the short code *99# from their mobile phone, irrespective of the telecom service provider, mobile handset capability or the need for a mobile internet plan.

How?

Fund Transfer using MMID and Mobile Number-

1. Dial *99# from your Mobile handset.
2. NUUP welcome screen will appear asking you to enter your 3 letters of bank's short name or first 4 letters of IFS code.
3. After entering valid Short name or IFS code, NUUP menu will appear with different options of available services enabled for your bank.
4. Enter 3 for Fund Transfer using MMID and Mobile Number and Submit.
5. A subsequent screens to enter Beneficiary Mobile number, MMID, Amount and Remarks (Optional) will appear.
6. Enter MPIN and last 4 digits of account no (Optional).
7. A confirmation screen will appear showing success response.

Fund Transfer using IFSC and Account Number-

1. Dial *99# from your Mobile handset.
2. NUUP welcome screen will appear asking you to enter your 3 letters of bank's short name or first 4 letters of IFS code.
3. After entering valid Short name or IFS code, NUUP menu will appear with different options of available services enabled for your bank.
4. Enter 4 for Fund Transfer using IFSC and Account Number and Submit.
5. A subsequent screens to enter Beneficiary Account number, IFS code, Amount and Remarks (Optional) will appear.
6. Enter MPIN and last 4 digits of account no. (Optional).
7. A confirmation screen will appear showing success response.

Fund Transfer using Aadhaar Number-

1. Dial *99# from your Mobile handset.
2. NUUP welcome screen will appear asking you to enter your 3 letters of bank's short name or first 4 letters of IFS code.
3. After entering valid Short name or IFS code, NUUP menu will appear with different options of available services enabled for your bank.
4. Enter 5 for Fund Transfer using Aadhaar Number and Submit.
5. A subsequent screens to enter Beneficiary Aadhaar number, Amount and Remarks (Optional) will appear.
6. Enter MPIN and last 4 digits of account no (Optional).
7. A confirmation screen will appear showing success response.

Source and more info: HERE

Hope it helps!