100 Bestbuy — refund

Address:

Chandigarh

sir,
I have shopped at 100 best buy i bought a tablet they promised it to send within seven working days .but they took a long time around 3 weeks and that also they did not send the same tablet that i shopped they said it is out of stock so they have send some other tablet ,it was not acceptable so i asked them what to do they mailed and said that return the tablet they will give me refund (i have their mails as a proof) they mailed that they have received it then i asked for my refund but they have not replied