Excuse me, what mobile phone can send more than 20 short messages at a time, or even more?

First, mobile phones support multi-party transmission.

Second, the SIM card also has this function!

Third, you mean "Fetion" when you send text messages by computer! It's a software, and texting is free. Download in Mobile official website. Download it to your computer and you can chat with your mobile phone (or download it to your mobile phone, only wasting traffic and not spending money)

Only 20 or 30 mobile phones can be sent, because the manufacturer didn't consider that someone sent more than 30 at a time. You can save the message first, then send it to twenty people, and then send it to twenty people. I'll report your mistake to the company, and I may get a result soon, hehe, but I can't solve your problem. sorry

I hope I can help you.