Before doing any coding, you need to design, design, design.
Spend an hour concentrating on File 1, and describing everything you'd need to do, as a human, to process each record so that it could be matched against File 2 if it were presented as the simple subscriber's telephone number (no country code, no local code, just their personal number).
Spend two hours doing the same thing with File 2, everthing you'd need to do to match that to the ideal File 1, doing it as a human.
Start getting to know your data. Know it well.
Don't think about programming yet. Think about how you'd need to manipulate the data. Make some good samples for both files. Make some expected output. Work out how you'd get from one to the other.
You may get to the stage that you don't think it can be done. Then post your findings here.
If you get to the stage of a solution, post your solution here.
The reason for not just giving you an answer is because the process of the deisgn is a really good exercise for you. Going through it will pay you back many times over in your career - if you learn how to do it.
There is an answer. See if you can find it. Once you have the answer, the programming is very easy. That's the point of doing the design.