Or, do what I do and give your phone number just one digit off, i.e last four digits be 1235 instead of 1234.
They can refuse to give you Gaia Cash if you lie on the forms.
Some offers, such as car insurance quotes, yes, you must put the right number. However, for offers that will never call you like surveys, I have never had a problem. I have completed and been paid for well over 50 offers.