Siri doesn't work on my cellular data connection

[magurele]

I recently bought an Iphone 5s (A1457) and I quickly updated the software to 8.4.1. The internet works fine, webpages load fast on 3G network, but Siri does not. Siri keeps telling me "Sorry, I seem to have lost my internet connection." while being on cellular data but it works just fine when I'm on Wi-Fi.
I also installed iOS 9 Public Beta 3 and guess what? Siri works on both cellular and Wi-Fi connection. I reverted back to ios 8.4.1 using iTunes and Siri is again not functional on mobile data connection. What can I do? Is it a settings problem?

 

[Bigeric23]

I had this issue, too. I called my carrier and it went away.

 

[magurele]

Thank you! Problem solved. they activated the VoIP service.