"False information given"

I called surgery on Monday to make a GP appointment as work was sending me home due to not being able to talk with blocked nose. Reception advised me that next available appointment will be following Tuesday. As I needed sick note I asked them will doctor be able to back date the sick note, reception said yes, I called again just to double check if this is really possible and they confidently told me yes. So its Tuesday I am going to see my doc and what they tell me is because we didn't exterminate you on Monday when you went off sick we cannot provide you with note.

But how can I get appointment on time if next available appointment is only week later.

I had no problem with information provided by my my doctor who was really helpful and supportive, but I am really disappointed with reception staff for giving false information, if they didn't had knowledge on this they should have gone and checked this information before advising their customers.