How to solve zoom problem of lg vu cu920?

I have a LG AT&T CU920 mobile and im facing a problem that my mobile is displaying a message 'INSERT SIM'  and the phone is not functioning.I had tried by replacing another sim but again it asking 'INSERT SIM'. 

This is not a bigger problem. The main problem is that your zoom button has become loose or totally gets damaged internally. That's why this type of problem is happening. You do not have to worry. It is a simple problem. As you have written in the question that you do not want to fix this problem on your own so I am telling you the method to do this question on your own. First if it is loose then you should open it and again fix it tightly and see whether it is working properly or not. If it is working properly then it is alright. otherwise you have to buy a new button of this model and then remove the older button and fix this new button on the place properly and tightly so that it is not loose. Now try to open the lg vu cu920 again. This time you will be able to open it correctly and I think or I must say that I am sure that you will not face any zooming problem.