My mobile contract is with telechoice. Will this work with an applewatch?

My mobile contract is with telechoice. I understand an Apple Watch will only work with Telstra/Optus/Vodafone. Will I be able to connect the watch to my telechoice phone but also use a Telstra sim in the watch so I can use data when not near my phone. Or is there another simpler option that I’m not thinking of. Cheers. Dan