If you're interested in upgrading from Tinder Plus to Tinder Gold, you can do so within the app. Open Tinder > tap the profile icon at the top of the main page > Settings > Get Tinder Gold.
Once you upgrade, changes to your subscription will occur within 24 hours or less and you will be charged for your new Tinder Gold subscription immediately. Apple should issue a refund for the remaining time that you had left on Tinder Plus.
For more details about the billing process, please refer to Apple Support.
Once you upgrade, changes to your subscription will be made immediately. Any remaining credit that you had left for Tinder Plus will be applied to your new Tinder Gold subscription. A new subscription renewal date will be assigned to you, and you will be charged for Tinder Gold on this date.
For more details about the billing process, please refer to Google Play Support.
Note: You’ll only be able to change the type of subscription you have (Tinder Gold or Tinder Plus), not the length of the subscription package. For example, if you’ve subscribed to Tinder Plus for 6 months and upgrade to Tinder Gold, you’ll only be able to upgrade to the 6 month Tinder Gold package.