Club 2 vouchers

Please give us an option to club 2 vouchers to book a trek. I had two vouchers, one from a cancelled trek in past, another from a difference amount between two treks ( RS. 1000 )

While I was booking the new trek, the two vouchers would easily covered the expense, but there is no such option provided. Now I am unable to use this voucher to even rent the gears too.