Message Blocking from Some Services Despite Not Signed Up for Blocking

I have three lines on my account. The user of one of those lines occasionally encounters a problem with some free services she's trying to access, where upon texting the service in question she receives a message "unable to send message - message blocking is active". A couple of days ago, I also tried working with a free service related to my employment, and received the same message when trying to text the service. The service was supposed to send me an initial text upon completing the setup on-line, but I never received such a text - I assume that was also blocked.

Per a tmo agent response on another thread (http://support.t-mobile.com/message/164722), I checked my T-Mobile account options. I confirmed that, upon checking both Individual and Shared Services, the only possible relevant service that is selected is "Block Content Downloads for Families". I looked at the "More details" information, and it does not seem that this feature should be stopping the texting services I and my other line-user are trying to access. No other services related to blocking are selected.

Is this a problem with my line that needs to be fixed somewhere? Are there other account options I should be looking for? Am I misunderstanding the scope of the "Block Downloads" option?

Thanks in advance.