visa for second enter into Tajikistan

Hello,

I have single entry visa to Tajik, but probably Ill have to enter Tajikistan again few days later (Tajik-Afghan-tajik). Is possible get additional entry in tajik visa at Dushanbe airport (I could organise it when Ill be first time at the airport) or in afghan Badakshan?
Tajik emabssy in Berlin- additional entry costs 10euro, what`s price in Dushanbe if possible?

thank you

To get an additional entry at Dushanbe airport, you'll need to ask for a new double-entry visa and cancel your existing visa. You can't have two visas at the same time.

Ok, so they can`t change only information from single to double ex. using stamp or something?