Can't Make a phone call - this is ridiculous

I have recently installed a LTE sim card and now am unable to make a single telephone call from my cell phone without it dropping/ cutting off the call on my side so I can't hear anyone.<br> <br> I have tried to call the customer care line and am unable to get through after holding for 30-40 minutes at a time and when I try to access the online customer care service to lodge my complaint I get an error message when selecting the link for the following page:<br> [URL Removed]<br> <br> How am I supposed to rectify this if I can't even get hold of MTN to assist me.<br> <br> If this is not resolved by the end of the week I am changing my service provider.<br>