Hi there!  @theartiszan‌ is correct, the warning that you're hearing advising of the fee is a recent update to something called "out of plan numbers".  You can read more about it here: Out-of-plan phone numbers FAQs‌, and we had some other users cover the topic with pretty great detail in this thread.  I think the suggestion for VOIP is worth a little more research - let us know if it works out!  Crossing my fingers that you're able to find a way to complete your calls that works for you.

- Marissa

Interesting there's nothing T-Mobile can do since I only get this (seemingly constant) charge notification on my T-Mobile phone but not on my "other" carrier phone.

So I have 2 phones...One is directly through T-Mobile (LG Stylo 2) and the other is through Straight Talk, it is a TracPhone on T-mobile service.  When I try to call conference number on direct T-mobile phone it says the number is out of call area and I will be charged 1 cent per minute but when I use the Straight Talk phone I have no issues calling in at all. This is straight up T-Mobile trying to charge their regular customers...this is how T-Mobile shows their loyalty to their direct customers, they charge them more. This is NOT the provider hosting the service this is T-Mobile.

I auto pay monthly for unlimited service, but it will not let me connect to a business conference call. 

The computer says that my prepaid balance is too low and will not connect. I would pay the .01 per minute if you would connect the call.

This is business, I need access to this number. I just used Google Voice instead for the one call, and they are pretty rare but this is too much to go through when you had one job - connect my call.

Very annoyed by this issue - please give me a resolution or I will be forced to change carriers.

This just happened to me this morning when I tried to join a conference line when I was able to join the same number on Monday with no issue. Very annoying because I need to join those calls for work.

I just left boost mobile and I had unlimited talk and text. I had no problem with getting on the conference call without any problems now I switched to Tmobile wants to charge that's a problem 

Just switched from Sprint.  I used the conference call line for business almost daily with no charges on Sprint.  On T-Mobile, they want to charge me even though I’m on their unlimited plan.  This is BS!!! 

I just used free conference call dot come and got the same message. I have no recourse as I have to be on this call. WTF Tmo, this could be the end of our 15 year relationship.

I doubt they even care.  They’re almost as bad as the oil companies!   One idea is to get a friend to merge you into the call on their line.