Problem with texting replies to automated service

When my work sends an automated text to my phone for shifts, I cannot reply to them straight away. Sometimes it can take 3 to 4 hours. The message bubble comes up green as it is to a non iPhone but the time doesn't show up either for message sent. I have to try and resend over and over at various intervals until it finally goes through. Very frustrating . I have tried all the " tricks " (turning messages and FaceTime off and on, resetting network, resetting phone,)but nothing seems to work . Can someone help or is anyone else having this sort of problem ?