You can certainly connect the eero to your switch. I assume that you do not have Digital Voice, what sort of phone is this? You cannot connect a standard landline phone to the switch, it would have to be a VoIP phone and you would need to subscribe to a compatible VoIP service.
From the 29th of March our TalkTalk Community will move to peer-to-peer support and the TalkTalk team will no longer be here to support with queries. Don’t worry we still have plenty of ways to reach out if you need to speak to TalkTalk directly. For more details check out the link here How to contact TalkTalk Broadband - TalkTalk Help & Support
