Dear Sir/ Madam
Ref: [nature of your complaint/reference number]
I am writing with regard to the above complaint. I wrote to you on [date] asking you to do [describe the action you asked them to take] to resolve this complaint.
Your attempts to resolve the problem have not been satisfactory and you claim that there is nothing more you can do to help me.
It appears that we have reached a position of deadlock.
Therefore, I am left with no alternative but to take my complaint to [Ombudsman Services: Communications /Cisas].
I would afford you one final opportunity to reconsider your position and confirm to me within the next 14 days that you will [describe the action you wish them to take] or alternatively send me a letter of deadlock.
If I do not hear from you within this timeframe I will refer this dispute to [Ombudsman Services: Communications /Cisas] with no further reference to you.