You can call Huawei's customer service number, which is also the most direct and convenient one. Then there is an official platform where you can file a complaint. You can check the Huawei cell phone three packages terms, you can also find the after-sales service manager, if you can not deal with can call 123I5 complaints.
The content of the complaint is also explained: you can give feedback and report all kinds of market and cooperation violations, such as unfair market competition, being treated unfairly, the manufacturer's personnel corrupt behavior (soliciting bribes, shares in dealers or positions, etc.), tampering, counterfeit goods, and so on.