I have an iphone se. I'd like the phone to default to my home isp whenever it is in range of the router. (or any other trusted data sites like work or school) I'd also like to manually turn on the Koodo data when needed.
Is there like a priority or default setting for iphone?
Pretty well any phone with wi-fi will connect to any saved networks if wi-fi setting is turned on in your phone, including your phone. Iphones also have a wi-fi assist feature to use device data if the signal is weak that you can turn on and off. You would hav to turn of wi-fi to switch to device data manually.
You can turn off data and manually turn it on when you need it Settings>Cellular
With Data turned off you will not be able to send picture messages (MMS) either.
If you want data off but still be able to send MMS, then you need to go to Settings>Cellular>Cellular Data and change the APN under cellular data (I personally just change the apn to sp.koodo.comZZZ). Leave the the MMS APN unchanged. Now MMS will work but data disabled (since the APN is incorrect). To turn back on, just correct the APN by removing the "ZZZ"