New customer. I send every morning to about 150 people a long sms (about 400 char). I send it about one every 5 secs. Not using group messaging software. At some point some sms wont get delivered. I do not have any !error and only know the message was not delivered by calls and received messages from frustrated people. Do I hit some kind of limit? (I have unlimited SMS plan) Those message are NOT unsolicited. I tried sending a 3 lines text message to my friend to whom I didn't send any message prior this morning and he only received 1 out of 5 of my messages. Same thing is happening with a different messaging software and a different phone with my sim card.
My phone is a LG G5 and I also tried on Galaxy S8: same result