Special characters such as Emoji can increase the number of credits required to send your text. This is somewhat complicated but here is the reason. A single text message has a 160 character limit. Modern phones and cellular carriers allow multiple text messages to be linked together and appear as one message on your phone. When this is done each segment is made up of 153 characters with the remaining 7 character-space being used to keep track of the order of each message segment. When using the standard encoding to send messages with A-Z, 0-9, and standard punctiation your message is encoded in what is called GSM-7 encoding. As soon as you add an emoji the entire message now has to be encoded in UCS-2 encoding. What all this means to you is now each segement drops to 67 charaters in length. Essentially, sending a message with Emojis will use at least twice as many credits as the same message without emojis.