The issue is with the Safari browser blocking the ability of the pop-up window to select send a SMS option.  


To resolve this use Google Chrome Browser - to download this to your iPad desktop follow the instructions contained in the link below:


https://www.google.co.uk/chrome/browser/mobile/


When you click on a mobile number (not the mobile symbol) as shown below: 


 A pop up will appear as shown below:



Select the 'Send SMS' option: 



Type your text message into the SMS window as shown above.  Click on Send to send. 


For step by step instructions on sending an SMS message to a contact please click here