641-715-3286

NOT FREE IF YOU HAVE T-MOBILE !
This is an access line for freeconferencecall.com but it is not free if you have T-Mobile.
When you call it, you will first hear a quick message "The number you are calling is outside the plan, and will incur a 1-cent per minute charge if you continue.  You can hang up now to avoid the charge."
That message is from T-Mobile, not the conference call folks.
There are discussions about this in the T-Mobile section of Reddit, and an explanation here from T-Mobile:
https://support.t-mobile.com/docs/DOC-33322
Not a fun surprise when you have to join a call with others, and there is no alternative - you're trapped.
Apparently neither AT&T or Verizon charge extra to call this number (per Reddit).