still no response regarding my data validation

i received a call yesterday from cellc but unfortunately i missed the call because i was in training i called back twice for someone to call me back but guess what i did not get a call, i am so fed up with cellc, can i give back your handset & cancel the contract because i had enough now, 2 months i have been struggling with this query & no one can tell me about my airtime, i received a report for april that make no sense after the 2nd call to cellc the agent advised me there is a april report i am seriously fed up with your service