I had just purchased a new cell from T-Mobile and - in the span of time before my old number ported - I got 3 calls from 823-2020 and 823-2021. I answered the third call and it was a phone survey from T-Mobile. Apparently, this number and others in sequence (-2020,-2021, etc.) belongs to Western WATS Data Collection (westernwats.com) in Ogden UT. Their direct line is 801-373-7735 for the in-house no call list.