Welcome to the Community, Oriander
As we are a “customers helping customers” forum, we do not have access to internal network tools or billing systems. For the administrative address issue, it is best to contact the hotline (0800 707 707) directly to verify the data in the system.
The switch to yallo is entirely up to you, but note that yallo uses the same Sunrise mobile network infrastructure. Historically, Swisscom simply has a different network density and grid layout as the former state monopolist. If the coverage in Windisch is currently affected by local antenna adjustments, the performance on yallo will remain the same.
Cheerio cosmo