Okay so, I bought this used iPhone 5s today and I found out it has a bizarre problem. It simply has trouble making and receiving calls. In the video you can see that it lags or something when I pressed dial, and once it starts dialing nothing happens (doesnt actually dial). I should add: - it receives calls but once the call is answered it will remain vibrating for an extra 10 seconds and nothing happens after. - the mic and speaker work well as I've tested them on Skype. - the phone reads the sim card as seen in the top right corner of screen. - it sends and receives texts perfectly fine. - 3g/4g works fine. - I've tried a hard reset and also restored the phone. - tried a different Sim card. I'd appreciate if anyone can help!