Problem solved. Not sure what's going on, but the following works:
Placed three commas after the first three digits in the telephone number string; make sure there are no spaces. Either it will work or a message box will appear advising that no connection was made and asking whether one is desired. Answer 'yes' and re-type all the data - this time commas are not required. Just don't forget that COM1 = ttyS0.
OG.