If you cannot change your phone number by yourself, you will have to:
1) fill the form https://wiki.wmtransfer.com/wiki/show/Phone_number_update#2
2) notarize your signature on it (means notary have to approve authenticity of your signature on the application form).
3) mail it via regular post in our office: 119049, 7 Koroviy Val str. Building 1, Moscow, Russia, Webmoney
All the documents received are checked for certification by a notary, so we need you to make sure that your notary speaks English or Russian. Also all the contact data of your notary should be stated in the letter. We need a web-site of the notary where we can find e-mail and phone number to contact.