Bad FTTH Service with no response upon termination

I informed them of cancelling my current FTTH service well in advance of their T's & T's but did not get any requested feedback of the actual line termination. I even escalated my requested emails to their Management but to no avail. I was cut off unexpectedly around 20:00 on 27/07/2021. I tried in vain to call them on 28/07/2021 only to wait about 20 minutes on my mobile call and be routed to the back of the waiting queue. Terrible service seems like a "fly-by-night" operation.