Cant connect to internet when WIFI is off

<p>I have been experiencing issues with my phone (iphone7)</p> <p>I have been to an MTN shop - changed my sim card, I phoned ********** - no help.</p> <p><br />I cant go onto the internet/send or receive watsapp messages/send or receive imessages etc. when im disconnected from WIFI. I even took my phoned to the Apple shop for them to send it away for repairs. No one can help me!!!!!!!!!!!!!!!!!!!<br />This is not a hardware error. I removed the sim card and placed it in my old iphone 6. I still cant go onto the internet/watssap. The phone is under warranty still.</p> <p>I dont know what else I can do. </p> <p>I want a new phone and new sim card that actually works!!!!!</p>