"Your Purchase Could Not Be Completed"

See the following Apple articles:

Add money to your Apple ID balance

Add money to your Apple ID balance – Apple Support (UK)

Payment methods you can use with your Apple ID

Payment methods you can use with your Apple ID – Apple Support (UK)

Hello shuaib194 ,

Go to Choose your country or region - Official Apple Support

You need to contact iTunes support for purchase issues.

- Select your country

- Then go down to the bottom of the page and clicking on Get support