Indian Railways — overcharge for a ticket

I bought a journey cum reservation ticket for my family at ajani reservation office from nagpur to ksr banglore. Pnr no.[protected]. For journey on 8.11.2017. I paid by debit card and was charge d. Rs 6030 for a3 (1adult m sr citizen 1 f sr. Cti and one adult citiizen).
On 18.11, 17, i went to ajani r booking offfice and booked my return journey
Banglor to nagpr pnr no[protected]. I paid by cash rs 4760 by rajdhani exp
For the same three people. Iwas shocked to see difference in cost for the
(Rs 1270) i want to know why this has happened? I also want you to return the differance.