Thank you for waiting, and I understand you are having trouble setting up Wi-Fi Calling and are receiving an error code. I can certainly clarify that for you.

The reason you cannot activate Wi-Fi Calling is that the PayGo plan does not include support for this feature. Wi-Fi Calling is reserved for our standard monthly plans. We recommend reviewing the specific features and limitations of your plan in the official terms and conditions document:

Terms and Conditions Link: https://www.ultramobile.com/mobile-plans-terms-conditions/.

感谢您的耐心等待，我理解您在设置 Wi-Fi Calling 时遇到了问题，并且收到了一个错误代码。我可以为您明确说明这一点。

您无法激活 Wi-Fi Calling 的原因是 PayGo 计划不包含对该功能的支持。Wi-Fi Calling 仅保留给我们的标准月付套餐使用。我们建议您查阅官方的条款与条件文件，以了解您当前套餐所包含的具体功能和限制：

条款与条件链接：
https://www.ultramobile.com/mobile-plans-terms-conditions/