Change the card in your Apple Account
Soco subscriptions are billed through Apple In-App Purchases, so the card on file lives in your Apple Account. Soco can't change it or charge a different card for you. To change it on your iPhone:
Open the Settings app.
Tap your name at the top.
Tap Payment & Shipping.
Tap the payment method, then tap Edit.
Enter your new card details, then tap Done.
Check the card you want now shows at the top of your payment methods.
This updates the card Apple uses for Soco and the rest of your App Store purchases. Apple's full guide: If you need to change or update your Apple Account payment method.
Enter card details only inside Apple's own Settings app, never in a link someone sends you.
Next steps
Your next question is probably one of these: