When declaring a struct you need to add a semicolon after the declaration, for example:
Also you've declared the data type being passed to your print function, but not its name. Use this instead:
}; <-- notice the semicolon
Try reading the compiler error messages, they are usually pretty handy at identifying the source of the problem even though its quite difficult at first.
void print(data currentdata)
cout<<"ID: " <<currentdata.id <<"\n" <<"Age: " <<currentdata.age << "\n" <<"Phone: " <<currentdata.phone;