Unknowns caller from Denver, CO

Class EVERY day at all times and never leaves a message

Repeated calls - most recent was today (Sunday) at 9:44 AM. Never leaves a voice message. Other numbers using same Caller ID include 720-600-6140, 720-315-7919, 720-507-2360.

I'm skeptical about their connection to the organization - these numbers do not match either the Denver headquarters office nor any of the local offices in the Colorado-Wyoming Chapter of the National MS Society. Even the area code is wrong. Reverse number search returns "owner identity hidden for privacy" in all cases.

To date, I have received 5 calls from this number with Caller ID showing Denver CO. Have also received numerous calls from two other similar Denver numbers, one of which was at 8:12 a.m. Never leaves a message. Per comments from other phone sites, this is a telemarketer for the MS Society. That's probably correct, as I donate to them because our daughter has MS. This is really annoying and I will be reporting them to the FTC. I don't care if they are a charity. They are a nuisance and are not permitted to call before 9:00 a.m.