You tried to buy a smaller plan while a bigger pass is running. For example: "You're on Creator until 30 November. Add more Creator days, or buy Week after it ends." Nothing was charged.
Your options
Tap the Credits box at the bottom of the sidebar to open Plan & credits (on a phone, tap the menu button (≡) at the top right first). Then:
To add days to your current plan, tap its button, such as Add 30 days. Its days and credits are added to your pass.
To move up, tap a bigger plan's button, such as Get Pro. You can do this at any time.
Smaller plans show After your pass ends and can be bought once your pass ends. Your end date shows at the top, next to Ends.
To add credits at any time, tap Buy under Top up: 100 credits for ₦1,000 or 300 credits for ₦2,700.