What makes you think that only happens with BT Mixture?
Not saying only BT. Just saying BT are pretty nonchalant in when it comes to post-sales support and that there are many other telecomms companies I would rather deal with before signing a contract with BT.... particularly a contract for a business customer.
I've a lot of experience dealing with BT and other telecomms companies, I've almost always found BT's post-sales support to be amongst the lowest of the low.
Anyway, PPRuNe isn't the place for this kind of debate so I'm not going to say any more.
