Most of the crosstalk problem comes from the A-interface and ater. It can be an cross-connected E1 or a faulty transcoding board. If I receive cross talk complain from customers I used to test every E1 between the MSC and BSC, one test call is enough for the whole E1 because if one timeslot is effected the others are also effected. It may take sometime to test 200 or 300 E1 but it is worthy and sure you will find the faulty E1 and then you can check the physical connection, and also the PCM number is very important both the MSC and BSC side must be the same. or you can replace the transcoding board and then make a test on the faulty E1 you find.