I can't download and install latest version of software for my iPhone 7

You are correct, your iPhone 7 can only update up to iOS 15, and not past that due to hardware limitations.

You can still upgrade your iPhone from iOS 14 to iOS 15, learn if your iPhone wont update ⇢

If your iPhone or iPad won't update - Apple Support

If you want the most recent iOS 17, you will need a compatible iPhone ⇢

iPhone models compatible with iOS 17 - Apple Support

You can also buy a new iPhone, as your iPhone no longer receives updates ⇢

• iPhone Upgrade Program - Apple
• Buy iPhone - Apple

For more information: Update your iPhone or iPad - Apple Support

-Zachyy ✌️

[Edited by Moderator]

The iOS version is not the cause of you not receiving calls. Many users are still able to use their iPhone 7 for phone calls. Your device does not have the Hardware capabilities to support iOS 17, but is certainly able to make phone calls. If you are having a WiFi issue, then start by restarting your router and provide more details on the issue. Specifically for issues with calls, contact your cell provider.

olujare wrote:

kept on saying not connected to internet despite connection to a WiFi

Connection to a Wi-Fi access point / router is necessary – but not sufficient – to get Wi-Fi Internet service. If the Wi-Fi network is not, itself, connected to the Internet, you're not going to be able to reach the Internet.

However, the ability to place and receive cellular phone calls does not depend on Wi-Fi service. As the others say, If your phone is working, you have a cellular plan, and you are within range of your carrier's towers, you should be able to place and receive calls just fine with iOS 15 and without a Wi-Fi connection.

olujare wrote:

Couldn’t download and install latest version of software for my iPhone to enable me phone out or receive calls, kept on saying not connected to internet despite connection to a WiFi

You can't make or receive cellular calls unless you are connected to the cellular network (or have WiFi calling enabled through your carrier).

Does the phone have an active mobile number?