The character limit for one SMS is 160 characters. If you need to send a message longer than 160 characters, it is possible to send multiple SMS together, formed as a single, longer SMS; this is called a Concatenated SMS.
To join messages together to ensure they deliver as one, a 7-byte concatenation header is used at the beginning of each SMS. Since this header is within the message, it reduces the total size of each SMS to 153 characters each.
Please also be aware that if you are sending in Unicode, your character count per SMS lowers to 70 characters for a one-part message due to the fact that each UCS2 character requires 2 bytes. The 7-byte header for concatenated messages will also apply sending in excess of one message. As a result, a two-part Unicode message has a limit of 134 characters and a three-part Unicode message has a limit of 201 characters.
How will I be charged for Concatenated SMS
If you are sending concatenated SMS, you will be charged as follows:
Concatenated Message Issues
If a user reports that the concatenated messages they are receiving on their mobile phones:
There are several reasons why a concatenated message (multi-part message) may not be correctly displayed on the handset:
However, it is important to note that the order of the MT message part can change several times during transit, right up until the MT message part is delivered to the handset. This is due to routing technologies, load-balancing systems and re-try cycles, all of which have an impact on the delivery of the concatenated MT message.