Though you have not explicitly mentioned whether these calls are ordinary Voice calls or WiFi Calls.
Ordinary Voice Calls:
If you are experiencing issues with certain numbers being barred on ordinary voice calls, the problem likely lies with your carrier. There is no inherent problem with your iPhone, as it can receive calls without any issues. The iPhone does not have a built-in call filtering option, so any restrictions or blocks are likely imposed by your carrier. To address this, you should get in touch with your carrier's customer support to resolve the issue. Additionally, if you have installed any third-party apps for call filtering, it's recommended to remove them as they might interfere with the regular call reception process.
WiFi Calls:
When making WiFi calls, the data packets of the call are routed through an internet service provider (ISP) before reaching the recipient. The ISP acts as an intermediary between your device and the cellular service provider's network. The cellular service provider is the company that provides you with cellular connectivity, while the ISP is the company that provides you with internet connectivity.
If the ISP and the cellular service provider are the same company, there is typically no issue with prioritizing WiFi calls. In such cases, the ISP understands the importance of WiFi calling for the cellular service provider's customers and ensures that the necessary quality of service (QoS) mechanisms are in place to prioritize these calls. QoS ensures that certain types of traffic, such as voice calls, are given priority over other types of traffic on the network.
However, if the ISP and the cellular service provider are not on good terms or do not have a partnership agreement, there is a possibility that the ISP may not prioritize WiFi calls from that particular cellular service provider's customers. This can lead to potential issues such as degraded call quality, increased latency, or dropped calls.
In situations where the ISP and the cellular service provider are not aligned, the ISP may treat all internet traffic equally and not prioritize WiFi calls. This means that WiFi calls will compete with other internet traffic, such as streaming videos or downloading files, for available bandwidth. As a result, the quality of WiFi calls may suffer, especially during periods of network congestion.
It's worth noting that the prioritization of WiFi calls also depends on the overall network conditions and the ISP's policies. Even if the ISP and the cellular service provider are on good terms, if the network is heavily congested, the quality of WiFi calls may still be affected. Additionally, some ISPs may implement traffic shaping or bandwidth management techniques to ensure fair usage across their networks, which could impact the prioritization of WiFi calls.
In summary, when the ISP and the cellular service provider are part of the same company, WiFi calls are typically assigned priority and treated with QoS mechanisms. However, if there is no partnership or disagreement between the ISP and the cellular service provider, WiFi calls may not receive the necessary prioritization, potentially leading to issues with call quality and reliability.
