I recently did a mass SMS send to a client's customers using Clickatell.  The messages were sent with a friendly non-numeric caller id (eg NATE) rather than a phone number.

All recipients on Vodafone received the message with this correct caller ID.

Some recipients on Telecom received the correct caller ID, others received it from a +44 number (Clickatell must've routed this message through the UK).

Anyone know the reason for this? Is it a per phone thing, or is it the network?  I'm really curious to see if it's not fixable from my end.