Just let the order be executed if you can not cancel that order, you have no other option, a little off topic, The price of bitcoin is very low in bittrex in relation to other exchange, I think this is related to the cases of blocked accounts without warning, maybe bittrex is having little volume in the BTC/USDT pair
Thankfully it got cancelled later on, they disabled whole ETC-BTC market for few minutes and than my order got cancelled when market reopened.
Actually USDT is quite stronger than USD right now, it is trading at above $1 so bitcoin price at bittrex is lower than in coinbase or other USD based exchanges.
problem solved locking thread....