By David Russell, reporter at OptionMonsterNEW YORK -- NII Holdings ( NIHD)has been bearish for a long time, but now buyers are betting that it's due for a bounce. OptionMonster's tracking programs detected the purchase of about 4,000 January 7 calls for 50 cents and 55 cents. Volume was 11 times previous open interest in the strike, indicating that new positions were initiated. Investors have now locked in a $7 entry price on the company, which provides wireless service in Latin America. The calls have the potential to generate significant leverage if the stock climbs but will expire worthless if the shares don't move. The stock fell 6.65% to $6.60 Wednesday and has lost more than 70% of its value in the last year. Short interest is more than 40% of the float, a potential catalyst for buying in the stock. Total option volume was 15 times greater than average in Wednesday's session. Russell has no positions in NIHD.