The telecom card I use can surf the Internet, but I can't make phone calls. What is the reason?

You can surf the internet with a telecom card, but you can't make calls with your mobile phone. If it is determined that there is nothing wrong with the operator's network, it is very likely that the telecom card is inserted into a non-full netcom mobile phone. Non-full netcom mobile phones can't make calls with CDMA. The main 4G frequency bands are FDD-LTE:1765-1780mhz, 1860- 1875MHz, and some of them overlap with Unicom 4G. Therefore, in theory, you can support Unicom's 4G dual Netcom mobile phone, and you can also use Telecom's 4 G to surf the Internet.

But what telecom uses for voice calls is CDMA network, which is dedicated to telecom mobile phones. Telecom's 4G card is plugged into a non-full-netcom mobile phone, and if the mobile phone can't search CDMA network, it will not be able to answer the phone. Because the patent of CDMA network belongs to Qualcomm, most countries and regions in the world have not built CDMA networks. CDMA networks are used only in Chinese mainland and the United States.

In order to save costs, some mobile phone manufacturers castrated the CDMA function of mobile phone baseband without paying CDMA patents to Qualcomm, and only supported mobile and Unicom network frequency bands. For example, if a user buys a Hong Kong version of Apple iPhone and plugs it into the mobile phone card of China Telecom, there will be a problem that he can access the Internet with 4G, but he can't answer the phone. As China Telecom is one of the three major operators, most of the mobile phones of Bank of China now support the full netcom function. Only a few parallel Apple and Samsung mobile phones do not support telecom CDMA.

Now, with the completion of China Telecom's VoLTE network, many provinces and regions have realized the function of 4G call, and LTE network can also be used for voice call without CDMA network. For example, the Hong Kong version of Apple's mobile phone is upgrading iOS.

12 system, you can use the telecom mobile phone card to answer and make calls. Some support dual card dual standby dual 4G.

VoLTE's mobile phone can even insert two telecom mobile phone cards at the same time, and both cards can make calls and surf the Internet.

But now China Telecom's VoLTE network has just been built, and it has not completely covered the whole country. Even in big cities, there are many dead ends without VoLTE network. Therefore, even with VoLTE, there is no guarantee that non-full-netcom mobile phones can normally use telecom cards anywhere. Therefore, it is best for telecom mobile phone users to choose to buy and use full netcom mobile phones.

In the future, when the telecom CDMA network is completely disconnected, there may be no problem that some mobile phones can't make calls with telecom cards. With the advent of the era of 5G network, this is entirely possible. Another situation is that the mobile phone card of the Internet of Things can't make a call. The user was greedy and bought a special mobile card for the Internet of Things on the Internet.

These telecom traffic cards are sold to enterprises, such as car networking equipment, vending machines, smart home appliances and so on. These IoT devices only need a function of surfing the Internet and do not need to make phone calls, so the phone and SMS functions of the IoT mobile phone card are cancelled. For various reasons, some telecom IOT mobile cards are sold online as normal mobile phone cards. I bought this card and plugged it into my mobile phone, so naturally I can't make a phone call.

Although the telecom Internet of Things flow card is cheap, it needs to be bound with equipment, so once the mobile phone is replaced, it may be locked and inconvenient to use. Therefore, this kind of Internet of Things traffic card can only be used on the iPad tablet, and cannot be used as a calling card for daily use.