Hello! I understand you're having trouble purchasing credit on the toovoip app using your Android device. Let's work through this together to find a solution.

To start, could you tell me a bit more about what happens when you try to purchase credit? For example:
- Do you see any error messages?
- Does the purchase process start but then fail?
- Are you using a specific payment method (credit card, PayPal, Google Play balance)?
- Have you tried restarting the app or your device?

Meanwhile, here are some initial steps that often help resolve purchase issues:

1. Check your internet connection: Make sure your device is connected to a stable Wi-Fi or mobile network. Poor connectivity can interrupt purchases.
2. Update the app: Ensure you have the latest version of toovoip installed from Google Play. Older versions may have bugs impacting purchases.
3. Clear app cache: Go to your device Settings > Apps > toovoip > Storage, then tap "Clear Cache." This can resolve temporary glitches.
4. Verify payment info: Make sure your payment method is up to date and valid for any purchases through Google Play, as in-app purchases typically go through there.
5. Restart device: A simple reboot refreshes your system and can resolve various minor issues.

If you've tried these or if there are specific error messages you see, please share those so I can guide you further. If all else fails, we might consider checking for any server-side issues or account blocks that would require support escalation.

How does that sound? Could you try these steps or provide more details on the purchase problem?