Well, they will call you at least two days in advance, I think it would not be difficult for you to go in that time, however, if they call and you are not able to move on, no problem, you can go for the next batch......
As for the fees, you need to pay it only when you are joining, just two days before joining the classes. So that is not a problem....
If you dont want to depend on the institute to call you, you yourself can call every 8-10 days to enquire about the classes, you don't need to tell them your name and no. everytime you call.. Just call up, ask when is the next GMCS batch, they will say yes/ no and then you can keep the phone and take your decision... I know they are rude... But we can't help, and we need to contact the institute through them only....!!