So, we are being forced to update, even if we don't want to, otherwise our text messages are throttled? Sounds like net neutrality laws are being broken. Regarding throttling, "No Throttling: broadband providers may not impair or degrade lawful Internet traffic on the basis of content, applications, services, or non-harmful devices." (FCC.gov open internet)
I have a right to not update, see: content; services. iOS updates are considered both of those, and it seems that this is a deliberate attempt to force us to upgrade to something we don't wish to update to. Thus, our "traffic" is being throttled. Text messages are small bits of data.
AND to still receive and send text messages. See: "Blocking: Broadband providers may not block access to lawful content, applications, services or non-harmful devices." (FCC.gov)
Services, such as text messages, are being blocked simply because I don't wish to update to iOS 9.1
Like I said, years on this forum and I have never seen a post in regards to throttled or limited abilities to send/receive texts be they in general or OS update-related. (outside of plan quantity limits and signal strength/coverage areas)
It's not either. We have the "MORE EVERY UNL TLK&TXT 15GB" plan and I have 4 bars from where I sit. I don't believe that San Diego is hindered in Verizon Wireless connection. All of my family members that have updated to iOS 9.1 are able to send text messages, so I do believe it's a Verizon problem. I was able to send text messages fine before 9.1 was released, and now I cannot.
Are you sending to other iPhone users with iMessage enabled? Make sure you're signed into iMessage if the answer to that is "Yes." Sometimes you may need to turn off and turn back on iMessage and Facetime.
iOS 9.1 should not be required to fix this problem, but is strongly recommended if you run older iOS9 builds in an effort to resolve a number of critical security issues. Additionally, you'll receive the latest carrier information by updating (this can sometimes be applied manually by going to Settings > General > About and click on the prompt to update the carrier settings if it appears. Note that outdated iOS will not receive these after a certain point). Do keep in mind, according to the software licensing agreement with iOS you must keep the OS up to date in order to receive support from Apple. Carriers can elect to enforce this same rule for troubleshooting purposes.
Since you're receiving texts, this tells us that your service should be working. In some cases, Verizon needs to rebuild the SMS/MMS portion on your line when one way texting occurs.