"We don't consider the increase in the cost of Outside of Allowance calls to be a materially detrimental change to your contract," Three offered.
Yeah? Well I'm making a counteroffer that reduces the cost of my Outside of Allowance calls to zero pence per minute. I don't consider that to be a materially detrimental change to Three either. Continuation of service after receiving notice posted to their head office will constitute acceptance of my terms.