Yeah, definitely you musnt loose hope. Having a somewhat low to average academic record in 10/12/Graduation, you still have fair chances of securing calls from some of the IIMs, particularly the newer ones as well as many other Colleges accepting Admits on basis of CAT like MDI, IMT, Old IITs and SPJIMR. Assuming youre a General Category aspirant, you must just target securing anywhere above 99 Percentile and youll have higher chances of getting shortlisted. Besides this, you must also appear for some of the Other Entrances like XAT, NMAT, MAT, SNAP which too are gateways to some of the Better B Schools of India.