Your SMS gateway service provider may restrict the length of the message that can be sent to a mobile phone. The SMSService will pass whatever information you place in the MSG keyword to the provider. It is your responsibility to ensure that the amount of data can be handled by the provider. Your provider will be able to advise you on any restrictions that they might have.
For sending messages to international mobile phones, the format of the number in the TO keyword will generally be a plus sign (+), followed by the country code, followed by the phone number itself. For messages to local numbers, generally the country code is not required although it will still work if you include it. You should confirm with your provider exactly what the required format is.
SEND TO(+6091234567) MSG(Test message)
SEND TO(+6091234567) MSG(Test message) CID(739) MSGID(97953)