The message character limit depends on the character bit-size of the alphabet you're using. For the standard GSM 7-bit alphabet, the character limit is 160. For an 8-bit alphabet, it is 140, and for a 16-bit alphabet, which sounds like your situation, it is only 70 characters. If you must send messages with special Unicode characters, like those in non-Latin alphabets, then you're stuck with the 16-bit alphabet, and its 70-character limit. If you can somehow convert the messages to the basic 7-bit alphabet, you will have the 160-character limit.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…