To my new bike!!!!!!

Last night I pretty much lost it in my cycling class.  Two times now I've had to bring my bike in for repairs.  I've not had it that long and it's just problematic right now.  The shifting is horrible, just does random shifting on its own, can't go into the big chain ring, the chain falls off..I could go on.
I've had to leave in the middle of two classes now and I'm pissed to say the least.  So once again today it's back in the local shop...lets see if the idiots can fix it this time..ughhhhhhhhhhhhhh