Hi, you installed a cable for my mother's neighbour, but the engineer decided for no good reason to wrap the cable over my mother's house's roof. She told the engineer to remove it from her property, he said he would and then left, leaving it as it was. My mother contacted you and informed you that you were trespassing and gave you until the 17th April to resolve the issue. You couldn't be bothered to reply or sort it out. Let me stress this as strongly as possible - you are trespassing on private land, you have been informed of this and asked to sort it out, and you have simply ignored the matter.
At this point there are several things you are required to do. Since he was informed he was trespassing, but left the cable as it was, your engineer broke the law. Is Virgin Media's policy that this is acceptable? If not, then obviously the engineer needs to face disciplinary action to demonstrate that you regard his actions as outside the scope of what you instruct him to do. If not, then you are admitting that you instruct your engineers to break the law, and obviously at that point I will be escalating this complaint. It goes without saying that we need to be informed of the outcome of that action in order for us to assess, frankly, the extent to which you find this behaviour unacceptable.
Secondly - you were given ample time to resolve this situation, I would have given you two days, not two weeks. You need to get someone over there to fix this immediately. If you only have one guy available and he's in Glasgow, then you need to get him to drive to Kent today. No further delays at this point are acceptable.
Lastly, I expect a letter of apology from a senior manager. You can't just trespass on a pensioner's property and then ignore their complaints and treat them with contempt. She is 78 and does not need this grief.
I hope you realize at this point that you are facing legal action. I suggest you resolve the situation while the matter is still in your control.