I don't know where you got news that economy is transitioned to bitcoins in bangladesh.Using bitcoins is banned in bangladesh.Even people are imprisoned if caught using bitcoins.
Got any more details on that?
In September 2014, Bangladesh Bank said that "anybody caught using the virtual currency could be jailed under the country's strict anti-money laundering laws".
https://en.m.wikipedia.org/wiki/Legality_of_bitcoin_by_country_or_territoryBitcoin is not a legal currency (legal tender) issued by any country. Bangladesh Bank or any organization of Bangladesh government does not approve any transaction of bitcoin or any other artificial online currency.
Bitcoin and it's transactions operate mainly through online network and it does not depend/approved by a central payment system, as such, people can be financially harmed. Transactions of these kind of currency could involve unapproved matters stated in Foreign Currency Control Act, 1947 and will be punishable by it. Moreover, users of these kind of currency will also be punishable by Money Laundering Control Act, 2012 for disobeying the stated act.
AFP also reportedly spoke to a representative from the bank, who said that the act of using a digital currency could be punishable by as much as 12 years in prison.
https://www.coindesk.com/bangladesh-outlaw-bitcoin-jail/