I can't figure out how to switch from 5ghz to 2.4 ghz

Your Wi-Fi router will need to be configured to provide separate 2.4 GHz and 5 GHz networks. That means that the 2.4 GHz network will have one name and 5 GHz network will have another.

Then, you set up the iPhone to connect to the name of the wireless network that you want to use.

So, the first question here would be......do you know if your Wi-Fi router has this type of capability? If you are not sure, give us the make and model number of your Wi-Fi router and we'll see what we can find out about the device.

If your Wi-Fi router was provided to you by your Internet Service Provider (ISP), they could be valuable source of information about the product.

AirPort Utility would only be used if you have an Apple AirPort Wi-Fi router. You can't use AirPort Utility to set up or change settings on a third party Wi-Fi router.

We only need the manufacturer name and model number of your Wi-Fi router. Please....do not provide a serial number for security reasons.

My ISP provides a Home Hub 4000 from Bell Canada with a Fibre Optic cable directly to Router

It can broadcast in the 2.4, 5 and 6 bands

In my setup, all 3 Bands have the same SSID name

We have 4 Apple Computers, 2 Cellphones, 1 AirPrint printer/ scanner and 1 MS Windows computer.

Some Devices located on upper level of the condo, some on main floor of condo.

Depending on the Signal Strength ( 2.4, 5 or 6 ) being received by any of the devices, a machine upstairs may automatic drop down to the 2.4 Band. This is because the 2.4 Band penetrates Walls and ceiling better that the other 2 bands

If I take that same device from upstairs to main floor and connect, it usually jumps to the Strongest Signal which is the 5 gHz or 6 gHz band

5 GHz and 6 gHZ bands generally works Best when Device and Router are in Direct Line of Sight and no objects in between

If you do not want to change names of the wireless networks and you do want to use the same name for both the 2.4 GHz and 5 GHz networks, then your Mac will automatically choose the network that it thinks is providing the best combination of signal strength and signal speed.

You have no control over this and will have to accept what your Mac thinks is the best signal.

As for alternatives, I see some references to “Bell Pods” as a means to extend a Home Hub 4000 Giga Hub for better coverage, and Telus has an Actiontec extender or two listed in some of their posted documentation. This is probably going to be easier, if you don’t want to acquire and configure your own extension, or your own set of access points.