The Speedport Smart (1) is suitable for VDSL connections with up to 100 Mbps. If you have ordered such a connection from o2, it will also work there. 
With regard to telephony, it is to be expected that the firmware of the Telekom Speedport Smart (1) does not support this at o2. Feel free to try it out and share your experiences with us. 

Thank you for your reply. Yes, I have ordered 100 Mbps, so good to know Speedport Smart 1 should work. I will try out the telephony and update here.

Thank you! 

After changing provider, please remember to perform the factory reset on the Speedport and set up the device for "Anderer Anbieter" with VLAN-ID=7 and with the user name/password provided by o2. 

Ok, I will do that. Thank you for the tip.

Hello @abhijithonline ,

welcome to the o2 Community .

It’s good to see that you’ve already received plenty of support from blablup. If you have any further questions, please do ask away. And if nothing comes to mind, then I hope to hear from you again after your connection is up and running.

Kind regards, Sven