can i still use my watch to make a call even if my iPhone is switched off.

Hi

Functions that are available on your Apple Watch Series 3 (GPS + Cellular) when it is away from your iPhone depend on various factors including:

• The features of your carrier service plan:
  • Apple Watch - Carriers - Apple
  • Make a call with Wi-Fi Calling - Apple Support
• The type of connectivity that is available to your Apple Watch at the time:

  About Bluetooth, Wi-Fi, and cellular on your Apple Watch - Apple Support

Features and requirements that apply under various circumstances are detailed here, including within footnote 2:

How to use your Apple Watch without your iPhone nearby - Apple Support

Whether or not calls can be made on your Apple Watch when it is away from your iPhone and/or when your iPhone is turned off depends on various factors, including the features of your carrier service plan, as referenced in my previous reply.

In the first instance, I suggest that you contact Sprint Wireless for assistance.

Keep in mind that, in order to use the built-in cellular feature, you need a carrier service plan for your iPhone that specifically includes support for Apple Watch Series 3 (GPS + Cellular), including the carrier activating it on the plan. An activation fee and ongoing monthly charges may apply:

Apple Watch - Carriers - Apple

How to use your Apple Watch without your iPhone nearby - Apple Support

In small text from footnote at bottom of article,

“

To receive SMS, MMS, or push notifications from third-party apps on your Apple Watch Series 3 (GPS + Cellular), your paired iPhone must be powered on and connected to Wi-Fi or cellular, but it doesn't need to be nearby“

So sadly, not as advertised, your phone has to be turned on, and connected to cellular/wifi, even when away from phone in order to work.

That's what it is supposed to be able to do....It's supposed to be able to make phone calls while not connected to your phone.

Footnote 1 in the article relates to messages, not calls (which are the subject of your question).

As previously advised, the text within the article - including footnote 2 - along with the other linked resources in my original reply explain the requirements that apply when making calls:

Jonathan UK wrote:

.. Features and requirements that apply under various circumstances are detailed here, including within footnote 2:

How to use your Apple Watch without your iPhone nearby - Apple Support