Binary coded decimal (BCD) is a way of storing decimal digits 0 through 9 using a binary form. BCD is often used with display devices with have limited or no processing capabilities. It is also used is a lot of telephony signalling protocols, like the GSM protocol you are working with. In telephony the two digits are generally packed in to a single octet, so when you see a value like 0011 0010, you need to evaluate the two 4-bit sections of the octet individually as two separate digits; not as one 8-bit value.
0011 represents the digit 3 0010 represents the digit 2