Unreachable

I booked a vehicle rental car through BA. My plans changed and I needed to cancel the vehicle rental. I called - no one picked up. I was on the line for about 15 minutes. I wrote on Twitter - I got a reply after a day, but they then went quiet again. I emailed and was given the number. The one that no one answers. I called again - still no one answers. I tried to reach BA on Facebook - no option to message. I tagged them on Facebook - no response. What other options do I have? I literally cannot reach them.

Never again...