Another possibility here is that BT outsourced the application development to a location in which the first language was neither US English nor UK English . Maybe the developers then failed to notice that the spell-checkers were set for the wrong 'customer', and nobody back home bothered to check, or couldn't be faffed with raising bug reports. Either way, I think agree with HP, if I understand him right. I'm a BT customer, and I speak UK English and not american English. It just smacks of 'every expense spared' to me.
In fairness to Razpag and other BT folks... I've said this before, but at a personal level ever individual I've ever met from BT have been absolutely ACE people, dedicated to their work as well as their customer and their employers. Real 'salts of the Earth'. That includes not just the guys who come to repair my phone, but also various professionals I've dealt with in developments at Martlesham in my working years.
But at a corporate level, when they can't even be bothered to spell-check an imported application, well I'm afraid that maybe they don't deserve these dedicated employees.
Just my opinion,
7LM