Changing network - old network name comes up despite factory reset - AC2200 Orbi Micro Router(RBR20)

> I've just moved house which has a different Wifi network to my old
> house. [...]

   What, exactly, does "Wifi network" mean to you?

> [...] my old network name keeps coming up when trying to set up the
> new network.

   Which "old network name keeps coming up" where?  "trying"?

> How do I overcome this?

   I don't know what "this" is, or what you're doing, or what's in
either house.

> Model: RBR20|Orbi AC2200 Tri-band WiFi Router

   Connected to what?  Is there an ISP involved?