When making or receiving calls on venu 2 plus, the call rerouts to iphone

When I have a call from the watch and while talking the calls ends on watch screen but the call is still actve on phone. It's like losing conectivity. Generally no bluetooth connectivity problems except while on call. I have tried everything (restarting devices, reconnection, unpairing/pairing, updating) but the issue is still there. I bought the watch 2 days ago and I' m extremely unhappy because calls are the main reason I bought it. My phone is iphone X.