When compiling your program the diagnostic LNC0810 should have been logged in the compile listing. This message indicates that the module name PGMA does not match the PROGRAM-ID of PGMB. The program name used is PGMA.
This behavior is documented in the COBOL Reference under ‘PROGRAM-ID Paragraph’:
The name by which the program object is known to the system can be overridden by the PGM parameter of the CRTBNDCBL command. The name by which the module object is known can be overridden by the MODULE parameter of the CRTCBLMOD command. See the WebSphere Development Studio: ILE COBOL Programmer’s Guide for more information on the PGM or MODULE parameter.