My Tablet drops calls, Samsung says no fault found

I have taken my Samsung Tablet in twice as it constantly cuts calls. Samsung on Hedrick Potgieter have tested it twice and they say no fault found. how can this be when it clearly is so.<br> they say there is nothing wrong. I cant use a useless piece of electronics that I am paying for every month.<br> how many times must I take it back, how many times are they going to say,,,,, no fault found.<br> It is not the Sim card or service provider as the sim works just fine in another phone.