Ok, here it is, a wee bug whist dialing.
There are some times I need to block caller ID for outgoing calls (e.g. business calls from home line). An so would precede the number with *67 e.g. *67974nnnn - The response would be "number not in service".

The way this was dialed was on a cordless phone where the whole number is entered first, then the off hook button is pressed. I then tried going off hook first, then dialed. This scenario worked, (however after some speed practise, I could also get this to fail too if I dialed the number fast enough).

So basically came to the conclusion that there needs to be some pause between *67 & 974nnnn

On further testing, I found this is also applicable to other service codes eg call forwarding - *72974nnnn. This creates an issue if you store such a number in the phones' phonebook for quick dial - it won't work. The solution is to program the number *72p974nnnn, then you can use the phones' phone book.

The other way that also seems to work is by adding the area code, e.g. *6709974nnnn, this too solved the problem, however I'm not sure if that would cause billing problems with being charged for local numbers?

Anyway, this isn't a big issue, and it may be something that is already known by WxC. If not, then I hope this is helpful as a workaround if anyone else has come across this too.

Thanks