The GSM standard specifies a maximum character length for each SMS message. These are ultimately determined by the carrier and the receiving mobile, but generally as a guideline
A message body containing only ASCII characters can have up to 160 characters
For messages that contain even a single character other than the ASCII character set, such as Japanese kanji, the maximum length is 70 characters.
Please note that a request with over-limit text will return Message too long.
Manage your message wise
You have to be careful when you send message text in English. Even if only one non-ASCII character is mixed into the text, the whole message will be regarded as non-ASCII message and the 160 ASCII-character limit will now be a NON-ASCII character limit of 70, and your request will get an error.
How do you check if your message is genuine ASCII?
There are various ways to check, such as this to check easily online.
Do test-sending that will be the best Please do test-sending, before you start the bulk message sendings.