When a persons money is blocked or has something less in value he goes to pawn shop. Than the best options for him is to do barter trade which keeps both parties in dealing with each other prosperously. They use to do barter trade in 1800's among every village, community & cities and it is best option for Iran after sanction's, who cares what United States says anymore.
Source https://www.dawn.com/news/1492420
