In my opinion, the two things (email from BitPay support and the unknown transaction) are merely coincidental and not related. If you did not initiate the transaction, then someone else has access to your wallet.
This would likely be because someone has access to your 12 word seed mnemonic... Did you ever store your 12 words in a digital format? (screenshot, typed in a text document, sent via instant message or email etc)? Did you ever type it into a website to claim forked coins? Did you ever give those 12 words to another person?
He did import the wallet when the others recommended him to do so in an attempt to recheck the funds if it was still there.
I have imported the wallet to another device with the 12 word but ithe problem is same i have also clear the cache and history but nothing change.
Another question I would like to add is which wallet did you use to import your address? Was it still Bitpay or different wallet ? because the transaction was created one hour later.