Microphone not linking to Whats App - not able to make or receive calls

I have recently bought an iPhone 6S - it's great.

But I'm having difficulties when uploading Whats App on the phone as it's not able to connect to the microphone so im not able to receive incoming calls or make outgoing calls from the app. I have also tried to send pictures from gallery within Whats App again not able to - but i am able to take a picture there and then and then send this one on the app.

When going onto Whats App to make a call then i get the following message "To place calls WhatsApp needs access to your iPhone's microphone. Tap Settings and turn on Microphone"

I have tried doing this but under microphone there is no options there at all in order to connect apps. I'm then getting this phrase under Microphone in Settings - "Applications that have requested access to the microphone will appear here. This is just a blank grey style page and is not giving any options to allow access here.

I have tried to do a hard re-set on the phone by holding down the home button and lock button and have also uninstalled the app and re downloaded it to try - no success.

Has anyone else had this issue and do you have any idea how to resolve the issue.

Thank you x