Huawei wireless modem can't send short messages.

I guess it's because of the annual fee. The annual fee is fixed, and the fixed fee is deducted every month, 12 months is exactly deducted. If you use it to send text messages or make phone calls, you will incur extra expenses, which will be deducted from your balance, thus affecting your internet access. If the balance in the last month is insufficient, then you can't surf the Internet in the last month. I guess Huawei deliberately disabled these two functions in order to prevent customers from making phone calls and sending text messages without knowing it. Of course, this is speculation if you are looking for a dealer to enable these two functions.