Reward payment

This company mdi-global run online surveys using an app called Refreshme which offer a drink diary surveys which run for 7 days and they pay R150 upon completion payments are processed every after 2 weeks so now they have delayed payments morethan 3 months now and they don't communicate with us as participants for me personally i have now done 3 drink diaries and 1 none drink diary survey the accumulated money is R570 which they must pay me but up until now they haven't paid me this people are using us