You calling a dog is not the same as the previous owner calling the dog, everbody has different pitch, levels etc.
If it's outside then when you feed it give the recall command YOU want to use as it comes into its bowl. (it's already on its way so you cannot fail). Do that for a week or so and then just extend it. when its out playing & coming towards you just give the recall command (it's already on its way so you cannot fail). Do that a couple of times each play session, praise the dog 7 then let it continue playing.
Then once you know it knows the command you can start it in a f