Unfortunately that 50 tk 1 GB internet Package is not available now a days. But they have few options for this 1 GB Data Pack plan. Those are as follows.
1GB 3 days`46 tk, to active, recharge 46 tk to your phone.
1Gb 7 Days 89 tk, to active, recharge 89 tk to your phone.
1 GB 30 days 189 tk , to active, recharge 159 tk to your phone.
and if you did not use GP internet for a long time, try this