Ex job CoS cancellation

Hello,

I have recently changed my job and advised my ex company to cancel my CoS, as I had a new one from a new company.
My ex company could not have an access to the SMS as a HR person responsible for SMS had left and nobody had credentials to get the access. HO told my ex company that it would take about 18 weeks to get new person registered with SMS.

The question is:

Am I supposed to contact HO and ask them to cancel my old CoS or leave it with the ex company as it is their responsibility to inform HO regarding end of my employment?

Thanks

It is the previous employers responsibility to notify HO that your employment has ceased.

No CoS to cancel as such as you have presumably already been issued with a new visa.