Message left on my computer after Norton IT assisted with installation

I purchased Norton 360 premium from Officeworks in Kew, Victoria, Australia two days ago.  I am trying to avoid putting my credit card details online.  I tried to load and in the end was redirected to Nortons where they were just about to take payment by Paypal even though I had already paid and had logged in with my product key.  I rang Nortons and was connected with a representative who I reluctantly gave access to my computer in order to assist me in this matter.  Nortons 360 loaded on my computer and my iphone.  Once she hung up, I have been left with a grey square midscreen with a recurring message box saying 'neagent wants to access key "Norton" in your key chain.  To allow this, enter the "login" keychain password, then click either 'Always Allow' , 'Deny'  or 'Allow'.  I cannot remove these from my computer - can any help please? I am on a Macbook Pro macOS Mojave. Thank you.

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I have tried rebooting and I have clicked on deny and it just flicks back up.

I think the grey square is left over after support session - any ideas on how I can remove?  It is permanently on my desktop.

I accessed phone number when loading - through help area somewhere along the way.  I did not search web for number and wouldn't trust.

Thank you.

Where did you get the phone number for Norton? If from an internet search, the first results are almost never genuine Norton Support.

Have you clicked on Deny? 

Have you restarted your computer?

It is possible that this was a leftover prompt from the support session that got hidden behind other windows, and it appeared once you cleared the other windows.