It's very likely these calls/messages appear to be the result of “call spoofing” -- a practice whereby someone disguises the actual source of calls/messages for malicious reasons. (You read more more about spoofing here at the FCC page on call spoofing.) The person engaged in call spoofing uses technology to display a phone number different from that of the telephone from which the call was placed.
Unfortunately, because the calls/messages are not coming from your account or from any other client within our vendor's ecosystem, there is nothing we or our vendor can do to prevent the behavior in this case.
Because the call/message was spoofed, there is no "trail" for us to identify in our records that the malicious number contacted your number.
Since we are able to take direct action and do not condone this type of malicious activity, I strongly encourage you to contact the FCC to file a complaint against the malicious number/caller so it can be added to their database. You are likely not the only person being affected and the more people who report these spoofing issues, the more it will help end this behavior.