For those who are on T-mobile (or any MVNO of T-mobile like MetroPCs) and can not get on conference calls, install Google Voice on your cellphones, and get a telephone number from them. Google Voice can work on your Android or iOS (iPhone) device.
Get one of these products, and use the same e-mail address that you use for Google Voice.
The cheapest device would be the Home Mini for $49.
Command your device to call into the talkcast number of your choice. i.e.:
OK Google: Call (605) 562-0400 (SASN / Free Conference), or
OK Google: Call (515) 739-1285 (FFTI / Free Conference Call)
When the prompt begins:
OK Google: “Press”, then say the access code or PIN#, and then say “pound”
i.e.: OK Google: “Press 5291816#” (SASN), or
OK Google: “Press 400014#” (FFTI)
If the call asks for you to introduce yourself, then say:
Your Name, OK Google #
Now you are on the conference call of your choice.