Any time I’m tryna purchase or buy something of download an app it says payment not completed

A possible reason for seeing this message is Apple cannot find a functioning payment method to use in making this purchase. You may not have the kind required or there may be problems with the ones you do have.

Use the document Add a payment method to your Apple ID - Apple Support to review your payment methods such as credit or debit cards. Problem methods will usually have a notice in red lettering below them. The article If your payment method is declined in the App Store or iTunes Store - Apple Support has some information about declined payment methods.

If using Apple Account balance to pay for an item, ensure there is adequate balance to pay for the item, including tax if applicable. Read this article about how to check your Apple ID balance.--> Check your Apple Account balance - Apple Support Some purchases may require the presence of another payment method such as a credit card even if the final payment will be made by account balance.

Also not this topic where a user reported an identical problem: App Store: suddenly Payment Not Completed - Apple Community

Providing a comprehensive listing of all possible issues and their solutions would be excessive in a single reply. If the information above does not indicate the nature of the problem then you may find the fastest route to resolution would be to accept the invitation to contact Apple for assistance with this.

To contact iTunes Support, do this:

1. Click on this link --> Choose your country or region - Official Apple Support

2. Select your country

3. Select: Billing & Subscriptions

4. Select: Subscriptions & Purchases

5. Select: Update payment method

6. Select a chat session or a phone call.