The prog code which causes PRI232 is 8A. M1 only supports 1, 2, 3, 4 and 8. 0A is not supported by M1.
Contact the CO to turn off the feature to stop sending DCH message.
0x81 0x01 1 Call is not end-to-end ISDN or may be in-band information
0x82 0x02 2 Destination call address is non-ISDN
0x83 0x03 3 Origination call address is non-ISDN
0x84 0x04 4 Call has returned to the ISDN
0x88 0x08 8 In-band treatment has been applied
0x8A 0x0A 10 Delay in response at the call interface