umm-salayum QTel really isn't to be blamed if you look at it this way.

You mistyped the number on a machine, machine does what its programmed to do - no mistake there.

The person that accidentally got the money should have atleast had the courtesy to call back and transfer the credit to your number. But then he might not know who sent him the credit coz you did it through a machine and not through your phone.

Qtel cannot help you even if its a genuine mistake coz from their point of view there is no way to determine if this was a unintentional mistake, unless they investigate into the matter by calling the person who you accidentally sent the credit to which might take days...so ask yourself is the 50 bucks worth is or just take it as a lesson learnt and forget about it. :)