Workplace harassment through emails and calls every day, despite isolating due to coronavirus

Good morning,

I was tested positive for Covid-19 last Thursday, and I was instructed by NHS via email and track and trace to isolate up to and including Friday 13th August. 

However, since I have been isolating, I have been bombarded with emails and phone calls every day. On the third of August, I was called eight times between 14:50 and 16:15, and I have been bombarded with countless emails, some with threats. I have been responding to the emails and I have informed them that, as a result of Asthma, Covid-19 has effected my breathing and left me breathless. I informed them that at this time I am unable to contact them all the time as I was trying to recover from a debilitating illness. My assistant manager in the responding email used the words "to escalate this" as some kind of threat. 

In addition, from employees I have spoken to my employer is spitting blood at me for informing colleagues I have come into contact with to isolate. Subsequent days later and they still haven't been informed by my employer to isolate. On the contrary, they have been told to carry on working. My colleagues only isolated when NHS track trace contacted them to isolate. My employers were deeply unhappy with me for doing this as they don't have employees to cover the duties. 

So, I need advice as to where I stand with my employers harassing while I am off sick and in regards to their threats. They are threatening me with breach of health and safety guidelines, despite trying to break the LAW themselves.