thank for reply..
my pic is working at 3.3v and modem at 4v.so why should i use level converter? i connected rx,tx pin of modem to tx,rx pin of pic.
and connected level converter(max232) parallel to pic(used only for watching in hyper)
i can send sms from modem to mobile.and modem can read the sms..but the response of the modem is not going to pic