Mive Style Folder 2 not calling?

I have tested 2 sim cards by 2 different providers. Initially they work and I can make and receive calls. But after a while (idk the exact time). Calls don't even come through and go to voicemail after a few seconds. Does anyone have had this problem before with the mivestyle or other phones? I have cleared the cache, that did the trick once but didnt work anymore after that.