Not knowing which make/model of router you have, there will be a device listing of currently connected devices when you log into it. However, if your neighbour is not connected at the time, it will not show in there. By far the best method is to change your WiFi password to something longer & more complex.
The TalkTalk Community has now moved to a peer-to-peer support model. This means that the TalkTalk team will no longer be here to support with queries. Don’t worry, there are 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
