24 hours transit without visa

Your situation is practically identical as the situation described by Cida Nanda Bora in the post below yours. I will just slightly adapt the answer already posted as an answer to his question:

First of all, you should count the hours of your entire transit through China. It is calculated from your first scheduled landing in China, in your case in Guangzhou and until your last departure from China, in your case from Wuhan. If that entire time that includes two layovers and the flight time between Guangzhou and Wuhan is less than 24 hours, you are definitely eligible for 24 hour visa free transit through China and you don't need any kind of visa.

You will have to print out your flight tickets and have the printouts with you ready to be presented to relevant authorities. During your check-in in Malaysia, you will declare that you will travel to New York via China using 24 hour visa free transit. You will also present your tickets and after a short inspection, you will be allowed to board the plane. Upon your arrival in Guangzhou you will apply for temporary entry permit because after Guangzhou you will proceed as a passenger on a domestic flight and you will literally enter China.

So, your itinerary seems fine, you should just calculate your entire time in China and if it is less than 24 hours, you will be definitely allowed to travel on your itinerary visa free.

By the way, the same is valid for your journey back and you should just reverse the order that I have already explained.

Just confirm with airline staff. Malaysian passport holder are not allowed for the TWOV

Quite the contrary... Malaysian citizens are allowed to use 24 hour visa free transit. I understand what you have done. You have called a customer care of an airline or an airline representative. All I can tell you is that they don't have a clue about these details. The only people that really know are airport staff because they can consult Timatic. The information you have received from an airline just shows how far their ignorance can reach. Shame on them.

Now, it's up to you to decide whether you will believe us here or an incompetent airline staff. By the way, if you decide to obtain a visa, you can do a check whether you are allowed to use TWOV or not. You can simply declare at your origin airport that you will fly using TWOV through China. They will, of course, see your visa, but you will tell them that you intend to use that visa for another transit through China. You will see that you will be allowed to board the plane. Also, upon your arrival in China, tell to the Chinese immigration authorities that you will use TWOV and answer the same thing regarding your visa. Then, you will see that you will travel TWOV and your visa will remain unused. Then, you will return here and tell us who was right in the whole story. Is this OK?

Zupan is quite correct: it is a complete waste of time and a total dead-end to call the airline call-centre in advance of travel. Even if they give you a verbal assurance that you're good to go, that is completely worthless once you get to the airport. And the check-in staff on the day will check your documents anyway, because the rules might have changed in the meantime. You can check the current Timatic through various airline websites, eg Emirates, Air New Zealand, and many others.

The problem is they don't even let us board the plane without a valid visa
And I also ask the visa processing center in Malaysia and the said need a visa
Luckily our flight is next week. Enough time for us to apply for a visa.
Actually I was in airport yesterday. Travel to other destination.
The airline staff also to me that Guangzhou airport had sent people back to Malaysia just a week back. As the same route as me because don't had a valid visa

They said TWOV only for those who don't not leave the airport
Cause us have domestic flight involved

As you most likely speak Mandarin I would recommend you to call immigration office at the airport for an difinitive answer. Anyone who had the (mis)fortune of dealing with Chinese bureaucracy on any level would be reminded that they play fast and loose with existing rules and the only way to get the most up-to-date answer is by calling them.