Try calling it using "procedure" and "parameterMap" tags. Example (more information here):
<procedure id="getEmpInfo" resultClass="Employee" parameterMap="getEmpInfoCall">
{ call getEmp( #acctID# ) }
</procedure>
<parameterMap id="getEmpInfoCall" class="map">
<parameter property="acctID" jdbcType="INT" javaType="java.lang.Integer" mode="IN"/>
</parameterMap>