There is no argument on your part. If they gave you a date or time period when the full services would or should have been operational, and if they have failed to keep that, they have lost. The LAW is VERY clear on your rights. If they have failed to provide the full services under the terms of their contract, you have every right to 'rescind' the contract. They are in breach of their contractual duties, it's that simple.

If you bought both elements (broadband and talkplan) at the same time as a packaged deal, then their failure to uphold either part would constitute a breach of the whole contract and entitle you to rescind the entire contract.

All you would require to do is send a letter to them (I would record delivery as proof), advising them that as a consequence of their failure to provide the full services you purchased (broadband and talkplan) that you hold them in breach of contract, and consequently you are rescinding the contract as of the date of the letter. Thereafter, refuse to pay them any money. I should point out that this is not even a requirement, but could save you some grief. The factual side is you could simply stop paying them without any notification as the way the law interprets this is, they already KNOW they are in breach, therefore they should know, or ought to know, that your failure to pay is a consequence of their breach - in this situation, the contract would become 'frustrated' and voided.

It would be a good idea to prepare something to replace your broadband prior to the plug being pulled on it, but after you send the letter, cancel all and any payments. You will not owe them any money, and it is extremely unlikely that they would attempt to pursue the matter as their legal department sift throught these matters prior to making a qualified decision. If what you say is true, their legal department would bin any attempts to pursue the matter, as in fact you could countersue them for the breach in the first place - your argument being along the lines (i'm presuming the talk plan offered you cheaper calls or some benefit of that ilk) that they have deprived you of a beneficial service which you ordered/ purchased and which they agreed to provide by a specified time, and their failure to provide that service may or may not have caused you some kind of loss or incurred heavier charges than what you would have paid if they had fulfilled their contractual obligations timeously.

Don't forget, that contract works BOTH ways.

This happened to me 6 years ago with BT, and unfortunately for them, it was for several lines. They PAID ME over Ł1600 as I was quick to point out their breach of contract. They had a scheme in place which provided X amount of pounds for every day which they failed to meet their deadline for each line, and it dragged on for weeks on end, hence the large payment. The guarantee scheme was nothing more than a quick fix legal remedy in their favour, which saves them money in legal fees.

From what i read, everything appears to be in your favour, and YOU could actually be the one who benefits here.

If you decide to 'rescind' the contract, then this is a mutual agreement to cancel the contract. If you simply advise them that you find them in breach of contract and that you no longer intend to pay for the broadband, you leave the door open for yourself to potentially benefit in the future.

Please bear in mind this is just an opinion based on the scant information you provided, and some other comments in the replies. If you are unsure or in doubt, citizens advice or a free legal services agency may be able to give you more qualified information if you provided them with full details of what took place.

If you have already paid them a fully year upfront, or for advance services and are going elsewhere, you could well be entitled to a refund or some monetary relief.