Confused by a delivery notification

I ordered some resin from a store in Australia which i often do since the exchange rate is pretty good for us in the uk (about half the marked price for us just now with shipping the same as if i posted something inside the uk) The part that has me confused is the notification came by text and I have no idea how they got my number as it is only linked to my emails, not my ebay account and never has been linked to it. I wish i understood technology better, lol