Bad service with new ford ranger 3.2 4x4

In March 2017 i purchased a ranger from McCarthy ford the glen Salesman was great and informed. I have trouble with a few items Navigation not working radio changing channels on its own Rear differential has a shudder And the roll bar is discolouring Vehicle went in twice for shudder and i was told it is normal....but if i put 3 baggs of cement on the loadbin it will go away.the rollbar was cut to fit the security lid and the dont want to change and the navigation still doesnt work after they tried to fix it 4 times.i also logged a complaint with ford sa with no response. I suggested they give me a loan car until they can sort the problems but was refused .