PAM DEMODULATOR

To 
all the guardians of signal processing,
iam writing a matlab code for the pulse amplitude modulation and
demodulation.
i have done in the following way
1.a sine signal with 1000Hz frequency.
2.then a square wave(carrier) of 10000Hz frequency.
3.multiplied these 2 for sampling.
4.quantized the resultant signal.
5.i have added some noise by using rand() fn.
6.at the receiver side i correlated the signal with the carrier signal.
7.i have interpolated the result using the function interpft().
8.then the output signal frequency is not matched with my first sine
wave,
%%%% IS THIS PROCEDURE CORRECT?
please suggest me what shall i do to get the original signal.