Paying for a 250/250 line speed but only getting 50/50

I moved to a new address at the end of March, and had my account moved to the new address and also upgraded my line from a 50/50 to 250/250. After some issues getting the line moved it was eventually activated at the end of April. But since then my line speed has not been wat I singed up for. When doing a speed test I was barely getting 50 upload and 50 download (not even close to 250/250 that I'm paying for). I logged a ticket for this on 10 May and had a few call back in the beginning to do speed tests and send the results but then they just stop getting back to me and I have called them again several times for an update, but just get told to do another speed test and send the results. My upload speed has been sorted but my download is still barely 50. And now when I called I was told the ticket was closed as completed even though it hasn't and no one contacted me to check if it was sorted or to inform me that it's being closed. And yet I'm being billed for a 250/250 line.