Can't cancel contract, can't speak to anyone, live chat not available and being chased by debt collectors for dead dads phone

I opened a contract for my father when he moved into a care home in May 2019. He couldn’t get to grips with it and didn’t use it. He passed away on March 29th. He hadn’t made or recevied a call for more than 6 months by then. I tried to call iD but this was in the grips of lockdown and couldn’t get through. I tried to cancel online but to do so meant having a PIN code texted to the phone and this was never returned along with his personal effects as the home said it was lost. I spent hours trying to get through to some one to sort it out but couldn’t so left it another month and cancelled my direct debit as I thought this was fair and equitable. Last month I was contacted by a debt collection agenct to recover the ~£10 that I ‘owed’. I explained the whole saga to the debt collection guy and he said he’d be back in touch if there was an issue. Nothing heard so assumed that it was all cleard up. Got a call today from a different debt collector saying I now ‘owed’ £15 and that the claim was issued a couple of days ago.  I am so sick of this now - It’s bad enough having to bury your father but to have to spend hours on the phone and internet discussing a £10 ‘debt’ is so infuriating. I was given a number by the debt collection agency to call - that turned out to be just  an automated line that took me round and round in circles and basically advised to get in touch via live chat. I hoped that my experience with live chat would have improved since my previous efforts but this time I couldn’t even find anywhere to access live chat. I have now wasted several hours of my life over a £10 ‘debt’ that I have absolutely no intention of paying now - it’s less than half of an hours wage but it’s now a matter of principal and the whole sorry saga is soooo frustrating.