EEOC -- Employer Equal Opportunity Commission
The Union
can a employer contact you while you are covered by a sick note
Certainly.
yes
Unions
Labor Unions
Contact your employer, they can change it for you. You most likely will need to contact the person who is in charge of payroll, as was the case w/my employer.
Contact your employer for a replacement.
What the purpose?
No
If your reference has a prior relationship with the potential employer then the contact would make sense. If not, no.
Absent a contract between you and your employer or local law/company policy stating otherwise, an employer may fire you for any or no reason with or without notice.