RM's privacy policy states:
"8.1. The company does not sell or rent your personal information to third-parties."
"8.2 Third parties do not have the right to access the Register unless required by the legal authorities (courts, prosecutors or investigative bodies). The law permits these authorities access to the personal data of the individuals."
If the information is coming from RM, some possibilities:
-RM sold your information, despite claims that it does not.
-RM lost control of your information, through hacking or mismanagement.
-RM gave your information to a legal authority, which may have lost control of it.
If the information is coming from RM, the second possibility seems most likely. You can always ask RM directly: "Why does a competing website suddenly have my phone number?"