Hi so i bought my tab about 3 weeks ago. When i boughtit, it had a mtn sim. So i changed it to cellc that evening and everything was cool. A few days ago i switched my tab on and it just showed no service. I have tried about everything and still nothing even swopped sims again. Im quite distressed over this as i dont have any idea what to do anymore. Please, please help me it is still showing no service