Why can I not purchase apps on my phone and why does it give me a notification that I have to have a card on it to purchase apps?

Cooroseloveme16 wrote:

Why every time I try downloading an app it doesn’t let me without having a payment method

Apple may require a valid payment method (which cannot be a gift card) for verification purposes. It may be charged a small amount to verify it but this will be automatically refunded.

Add a payment method to your Apple ID - Apple Support

and won’t let me change where I’m from to make it work. I don’t understand.

Changing your region requires that you've done all of the below:

• Spend any balance remaining on your Apple ID. If you're not sure whether you have a balance, check your Apple Account balance.
• Cancel your subscriptions and wait until the end of the subscription period. 
• Wait for any memberships, pre-orders, movie rentals, or Season Passes to complete, and wait for any pending store credit refunds to process. You can cancel a pre-order.
• Make sure that you have a payment method for your new country or region. See what payment methods you can use.

Change your Apple ID country or region - Apple Support