Routers do not keep changing bands, they broadcast on both bands at the same time.
Splitting the SSIDs DOES NOT disable the Sagemcom feature called WifI Optimisation which changes the CHANNEL within the band which can cause issues.
Only staff here can disable that, just request it in your next reply.
Here is the article on how to split the SSIDs to give them different names.
https://community.talktalk.co.uk/t5/Articles/Split-your-router-s-SSID-wireless-network-name/ta-p/230...
