I followed exactly the described procedure but it doesn’t work for me neither! In consequence no telegram usage is possible over mobile network because telegram seems to rely on IPV4. Android app firefox instead works.
Edit: This thread could(!) be a double post / duplicate to Unable to use mobile data on Sony Xperia 10 III 4.4.0.64 - #49 by akikyo
Edit: … or [4.4.0.64][Xperia 10 III}VoLTE conflicts with mobile data