Yes, SMS can be used as admissible evidence in the light of Section 65 B of the Indian Evidence Act. According to the aforesaid section any electronic information which has been printed on a paper, stored, recorded or copies in optical or electric media produced by a computer shall also deemed to be a document. Electronic records have been given a legal recognition by way of Section 4 of Information Technology Act, 2000. The apex Court of India has accepted electronic records as admissible evidence in the case of State of Delhi v Mohd. Afzal. Similarly in State v Navjot Sandhu the court has accepted electronic records as secondary evidences where the original copy of the message is printed out by the prosecution. So, in the circumstances of your case you can very well use the SMS as a proof that A has taken money from you and it has yet not been returned. Moreover, you shall also try to substantiate your claim by other evidence such as bank passbook copies of money transferred, etc. Further as per Section 85 B of the Indian Evidence Act, there is a presumption as to authenticity of electronic records in case of secure electronic records (i.e. records digitally signed as per Section 14 of the IT Act, 2000. Other electronic records can be proved by adducing evidence and presumption will not operate in case of documents which do not fall under the definition of secure electronic records.