Need help using iPhone 4 with TracFone BYOP

I was given an iPhone 4 and have tried using it with the BYOP TracFone network following the instructions on their website. Mostly everything is good EXCEPT I can't send a message or text to more than one contact at a time. Also I cannot receive anything from someone who has sent the message or text to me and others. I checked the MMS setting and it's on. I can't check the APN settings. They just aren't there.

Of course I have tried calling on TracFone help both online and over the phone and they said I need to contact Apple...

Does anyone here know how I can fix this? I know I can just send to one person at a time, but have no control over others who include me in messages they send out to more than one person at a time.

This is my first time posting a question on this Forum so if you need any other information, please let me know.

Thanks in advance for you help!