Titan watch - Depreciation Voucher

I had given my Kenneth Cole watch for changing the glass since it was broken to Titan service. But, they said they wouldn't be able to repair it and they would provide with a Depreciation Coupon for **% of the original value of the watch since the watch is more than * years old. I was not happy with this since they forcefully made me to take the voucher and said that's the only solution they will be able to provide. Also when asked how did they arrive at **% only since the watch is in good condition only the glass needs to be changed, they said take the Depreciation Voucher or leave it. Since I did not have any other choice, I had taken the Depreciation Voucher for the sum of Rs. **** and was informed that I can buy anything from Titan. But when I go to the store, they said I can't use this Depreciation Voucher only for Titan Watches and no other brands and that too I cant use this Voucher for any products that is on discount. I wanted to buy a Titan Smart watch which has MRP of ***** and with discount its Costs Rs ****~. The store person said that he will only reduce from the MRP and not from the discounted money. When I said this is a Depreciation Voucher and not a Discount coupon or something store Manger said he cant do anything and thats Titan policy. What I am asking is Depreciation Voucher is like having cash with me and how can you say that this Voucher cannot be used. Also how can you sell a product for once with discount and for other without discount in the same store. This is clearly cheating the customer. Very poor customer service from Titan