I don't know. How many years ago and have you a receipt? As its a padlock a hacksaw or a bolt-cutters will snip through the shank in short order. If its on a garden shed you will probably be able to remove the screws holding the receiver for the bolt with a screwdriver. Personally, I wouldn't go to the expense of calling out a locksmith.
To keep keys like these lubricated, rub the shank and the teeth with a pencil. Graphite is a great lubricant, but not for keys with electronic components e.g. car-keys