Unable to call a specific contact on iPhone

To improve my understanding of the phenomenon, it would be highly beneficial if you could share a full screenshot (Do not crop it). Visual representations carry a greater impact than written descriptions.

Please remember that this is a public forum, so when attaching a screenshot, please avoid including any personal credentials such as IP addresses, card details, email IDs, Apple IDs, IMEI numbers, serial numbers, phone numbers, order IDs, or any identifiable location information if you are sharing a map.

With the limited information that you have provided, It is hard to even guess the problems faced by you. 

You may get faster and better responses to your query by --> Writing an effective Apple Support Commun… - Apple ...

Please re-post with detail so that someone else can help.

In the event that you are unable to establish contact with a specific person, the following explanations may be considered:

1. Out of Network Coverage: If the person is outside their cellular network's coverage area, their device may not be reachable for calls. This could happen in remote areas or places with poor network reception.
2. Blocked by the Recipient: If the recipient has intentionally blocked your number, your calls will not go through. This is a user-specific action and not related to network or SIM issues.
3. Network Issues: Temporary or localized problems with the recipient's cellular network, such as maintenance, outages, or high traffic, can prevent calls from connecting.
4. SIM Deactivation: The recipient's SIM card may have been disabled due to issues such as non-payment of bills, SIM card expiration, or actions taken by the carrier (e.g., a stolen phone report).
5. Service Expiry: If the recipient's prepaid service has expired, they may lose the ability to receive calls until the account is recharged.
6. Number Change: The recipient may have changed their phone number and forgotten to inform you, resulting in your calls not connecting to their new number.

Key Takeaway: Except for being blocked or a number change, all other issues are related to the recipient's cellular network or SIM functionality. Each scenario should be considered when troubleshooting.

What Call? On an iPhone, you can make and receive various types of calls. Here are the different types:

1. These are standard voice calls made over the cellular network. They utilize your carrier's voice network to connect you with other phone numbers. Allow phone calls on your iPad, iPod touch, and Mac
2. FaceTime Audio allows you to make voice calls over Wi-Fi or cellular data using your internet connection. It provides higher audio quality compared to traditional cellular calls.
3. FaceTime Video enables you to have video calls with other FaceTime users. It uses the front or rear camera on your iPhone to transmit live video during the call. Use FaceTime with your iPhone or iPad - Apple Support (IN)
4. VoIP (Voice over Internet Protocol) calls use internet connectivity to make phone calls. Apps like Skype, WhatsApp, Viber, and Google Hangouts utilize this technology, allowing you to make voice and video calls over the Internet.
5. Some carriers support Wi-Fi calling, which allows you to make and receive calls over a Wi-Fi network instead of relying solely on cellular coverage. This can be useful in areas with weak cellular reception. Make a call with Wi-Fi Calling - Apple Support (IN)
6. The App Store offers numerous calling apps that utilize different technologies. These apps can provide additional features and options for making calls, such as international calling, call recording, and more.

It's important to note that the availability of certain call types may depend on your iPhone model, iOS version, and carrier.