There are several points concerning SMS that need to be clarified to avoid issues with billing.
Limited number of characters
The number of characters in a ashort message is limited. If a message is longer than that, it is automatically split into several messages. Each message is billed individually.
Character encoding
The number of characters in a message depends on the type of encoding. The standard Latin alphabet encoding(GSM03.38),used for English and some other European languages, includes a limited number of characters. If only these characters are used, then the message is 160 symbols long. But if at least one non-standard character is used, even accidentally, then the whole message is re-encoded and shortened up to 70 characters. As a result, the number of messages to be sent will increase, and the billing will increase accordingly.
To avoid this situation, it is key to use only standard characters. Here is a table of acceptable GSM 7-bit default alphabet (taken from https://en.wikipedia.org/wiki/GSM_03.38).
**L ** is a Line Feed control.
**C ** is a Carriage Return control, or filler.
**ES ** is an Escape to extension table (maps to NBSP).
**S ** is a Space character.
**F ** is a Page Break control. If not recognized, it shall be treated like LF.
**CR ** is a control character. No language specific character shall be encoded at this position.
**SS ** is a second Single Shift Escape control reserved for future extensions.
Note
It is very easy to pick up a wrong character by mistake, for instance, when copying the text from Microsoft Word, especially minor characters, like‘ (apostrophe) or “ (quotation marks). Yet, if this happens, the system will react with a warning before sending the SMS.