Dear George,
After analyzing your code I can see that there is a client action "PhoneOnChange" associated with the On Change event of the input boxes for both Mobile and fixed line. This action is creating the issue, as it re-assigns the variable with null values when you are inputting any value in any of the inputs.


There is basically no need for this action as the value gets assigned automatically to the associated variable of each of the input box. You do not need to assign it separately.
remove this action from the event of both the inputs and your code should work fine.
Cheers !
Shounak