Q: I keep trying to put my payment details into my new apple id however my payment method keeps getting declined

What are you trying to use as your payment method, credit or debit card ? If it's a debit card then that might be why, not all seem to still be accepted, and they might no longer be accepted at all in some countries.

For a card to have a chance of being accepted it needs to be registered to the same name and address (including format and spacing etc) that you have on your iTunes account, and have been issued by a bank in the country where you are (and therefore the country which is on your iTunes account).

Being a debit card might be why. Do you have a credit card that you could try ? Or are iTunes gift cards available in your country to use as your payment method ?

To create a new account without giving a payment method : Create or use your Apple ID without a payment method - Apple Support

iTunes doesn't appear to accept all debit cards - and in some countries debit cards may not be accepted at all.

The decline message may also be as a result of the card issuer declining it for use with iTunes, it's not necessarily at Apple's end

You've contacted your card issuer, they've confirmed that it's not at their end ?

If they have, then you can try contacting iTunes Support via the 'contact us' link at the bottom right of every page on here, but (if the details on your account match, exactly, the card's registered address, and the card was issued by a bank in your country and therefore the country on your account), you are very unlikely to be able to use it with iTunes