It may be due to loose contact. Try the following: Remove the sims. On the back of each of the sims place two layers of thin cellotape or packaging tapes.Trim the edges. Now insert the sims. Also place a thin hard strip of plastic ( even a match stick piece) in between two sims so that they do not slide out. Over this, again put a piece of cellotape See now your sims will work, unless of course the phone other has major issues. Dr Sundara