Tech Visit Scheduling Issue

I might as well post this here because it's as good a place as any.

Recently one of the VM forum staff booked a tech visit to try to resolve an issue I've been having. I was due to be working on the East Coast of the US and the appointment was made for the day I returned home. Thinking I'd likely be a bit tired, while I was in the US, I decided to reschedule the appointment through the link provided in the original email.

I rescheduled and took a screenshot of the new appointment time. As expected, no technician turned up on the day, despite me taking a day off work to be home. I got a reminder the next day that a technician was due to visit, unfortunately due to personal reasons I wasn't able to be available for this so I let the original guy know via PM. I also explained that there must be an issue with the booking system because the date that was confirmed to me, didn't tie up with the date Virginmedia had a note of on their system, I explained that potentially it might have something to do with the fact that I was on the East Coast of the US when I changed my appointment and so my timezone(and time) was set accordingly. The guy from Virgin Media pretty dismissed this out of hand, calling me a liar in the process, so I decided to test. I set my timezone settings to US Eastern, rescheduled an appointment for Friday 15th September between 08:00 and 12:00 and the screenshot of the resulting confirmation is shown below, clearly showing the date as Thursday 14th September between 08:00 and 12:00. I suppose the time is correct so I should be thankful that they can get something correct, just not the date!!!

Far from thanking me for bringing this to their attention, finding the resolution and leading them through it by the hand, rather than admit their mistake, they're now sating they can't guarantee I won't be charged for the appointment they made for the wrong date, 'it'll be up to the field team' apparently.