How can I get my Straight Talk Iphone 6s to recieve certain

Hi,

I receive calls from everyone else but two of my daughters have T-Mobile and my I Phone 6s which I activated for Straight Talk will not receive their calls or texts. They are on Separate plans?

Please help.

I didn't find the right solution from the Internet.

References:-

http://www.tomsguide.com/forum

example of case study

Thanks