Thank you sterling r, I have also tried the said with the support of the Apple Support team: Contact Apple Support via iCloud backup and through iTunes and the problem is still unresolved. I am still unable to make or receive any calls. I am receiving all forms of SMS but no calls. My phone rings but I am unable to answer, when I try to make a call the receivers' phone rings and they are able to answer and no sound comes from phone phones, my speaker is also greyed out. I am able to watch YouTube videos, browser the internet and every other thing as per usual. Sometime when I try WhatsApp calls it rings their phone also and when they answer the call ends (call fail message shows on my phone) and at other times it says you cannot place a call you are already on a call.