The sentence is grammatically correct. It conveys that the speaker received a Samsung Duos phone as a gift from their uncle due to achieving a distinction in their junior WAEC (West African Examinations Council) examination.
Here are a couple of possible rephrasings:
1. "I had a Samsung Duos, which my uncle gifted to me for achieving a distinction in my junior WAEC examination."
2. "My Samsung Duos was a gift from my uncle, given to me in


