I'd like to understand the routing involved in connecting from my mobile phone to an 0870 number. My belief is as follows:
My mobile connects to the local (Orange) mast which routes the signal to the local Orange digital switch via copper/fibre. This switch recognises that I want a landline so it connects me to the nearest BT Trunk exchange (rather than the local BT exchange used by landlines). The Trunk exchange switch recognises that this needs special processing and so passes the call through to the special 08** processing systems (for special charging/routing etc) which then route the call to the destination local exchange switch via the BT Trunk.
Or does the call stay on the Orange network until it gets close to the 08** system?
Or am I completely wrong?
Does anyone know where I could look at any diagrams that illustrate this routing?