The actual number displayed was ... 5-915-535-2894

Went to voice mail while we were not home... a guy was saying Hello to the recording... but definitely heard what amounted to a 'boiler room' in the background.

A female voice could be heard saying that... if her listener would just give her 5 minutes for her to explain..

915 is a west Texas area code... but the 5 in front of it (instead of a '1' for long distance) confuses me.
could this be an offshore boiler room tapping in to a west Texas exchange through the internet ?

Describing this as a telemarketer is my best guess
Nothing came up for an actual company  name in a Google search of the number