ATT Numbersync

NumberSync supposedly does work over Wi-Fi with the Apple Watch, but there are a few caveats - it has to be on a known 2.4GHz Wi-Fi network. The person in the store might have been thinking of the way that the Samsung smartwatches work - they have a cellular radio in them and their own phone number (and charge) on your account, so you could use them for calling even if you're away from Wi-Fi.

Further reading: https://discussions.apple.com/thread/7379074?start=0&tstart=0

 

You should almost always trust the website over the rep.

I had a similar experience where Apple's website shows the Verizon, AT&T, T-Mobile, and SIM-free iPhone SEs as all being the same model number, so any of those unlocked models should work fine on any of those other carriers. So when I tried to buy an AT&T model to use on Verizon, two of the reps told me it can't be done and wouldn't sell me the phone on the payment plan (the one Apple offers, not the carriers). Luckily for me, a third rep actually knew what she was talking about and confirmed it would work fine, which it did.

 

Yes, NumberSync works on my Apple Watch, but it's only 2.4ghz networks I think.

Also, remember that NumberSync doesn't not support SMS/MMS. It's just calling.

An iPhone can SMS/MMS over WiFi.

 

i tried the sms with watch with iPhone turned off on t-mobile , and my watch couldn't send it, darn
i noted that voice dictation now works . it didn't work before

 

Yeah, calls can be made even with your phone off, but texts are sent to your phone through an Internet connection, and then the phone sends the text from there.