[mothered]

Been 10 days since it was delivered and signed for by Garmin.

What Information was on the consignment when It was signed for?

Been in contact this morning and they asked for my tracking number.

On receipt of giving them the tracking number they are satisfied that my item has been returned and have no processed the return. Replacement has been dispatched.

Given they didn't have the tracking number to begin with, how did they verify the shipment was In fact In transit and returned?

Or did they base the return purely on the consignor and consignee details?

Also interested to hear your method in more detail. Please share

I assume the return was confirmed solely with the tracking details.

We'll see what the OP has to say.