Terry,
As a European and as a person who running a company here I can tell you that there is no new European law which would require them to have your phone number.
There is a new law called GDPR which requires them to ask you if they can hold and handle your personal datas (like your email, phone number, date of birth, living place etc.), I mean the new law says that they have to inform you if they will store any of your information and they must inform you how they will use your datas when you give your datas to them. For example if they will ask for your phone number and will sell that information to 3rd party companies then they must tell you to who and what datas they will give out etc. They must tell you this when you giving them that information. So you then aware that this company will collect your phone number to store and to sell it to some companies.
Furthermore if you asking them about what data they have about you and if they have any of your datas then they must inform you about that when you asking. And if you not consenting to store your datas anymore then you can ask them that you don't consent anymore and then they must erase your datas in their system.
So, the new European law is nothing about that they must have your phone number, instead it is about that they cannot have your phone number or other personal informations without your consent.
The new law is to protect the consumers' privacy and not to get more information about them without their consents.
And the new law is really a bit stupid in many points, it is so restrictive to companies that it is kind of stupid.