Vegeta almost always addresses Goku by his Saiyan birth name, Kakarot, but has on rare occasion addressed him as Goku. Vegeta says Goku’s name eight times, only two of which stating that Kakarot is Goku.
The first two were before he realised that Goku was Kakarot, during his battle on Earth, and the third is when he said Goku must be Kakarot. The fourth was when he was healing in the rejuvenation tank during the Namek Saga.
The fifth and sixth was during the Garlic Jr. Saga, when he is searching for Goku, he referred to him as Goku when speaking to the Frieza soldiers twice, perhaps figuring that if Goku had come across them and introduced himself, he would have used his Earth name (though this is not to be so easily dismissed as non-canon, the moment after Garlic Jr. is sucked into the Dead Zone, Vegeta calls him Kakarot again).
The seventh time was in “Welcome Back Goku” when Vegeta says to Trunks “Kakarot, the one you call Goku, and I are the only Saiyans left.” The eighth time was during the Super 17 Saga, when he was incapacitated by Super 17, Dr. Myuu boasted that no one could stop them with Goku trapped in Hell; Vegeta immediately regained consciousness and shouted, “Did you say Goku?!” Additionally, in the original manga, Vegeta once refers to Goku as (Son) Goku after being shown his full power during the opening match of the Cell Games (after Satan lost his) when remarking at the extent of his true power, and Vegeta refers to him as Goku aloud when he asks for Dende to wish that his power be restored to full strength.