with a network the size that you describe your 4 E1’s will not by themselves be causing congestion (unless the inter EWSD trunks are extremely under provisioned). Please see point number 1) of my first reply to you on 13th April – the carrier may be trying to cut back other sources of traffic and not only your traffic.
Also please see every other posting including the first in which I mention possible commercial issues. From the wording of your postings (you express doubt that such a large network could suffer from the problems that have been described to you) it would appear that you believe some form of commercial issue is the real reason for the carrier attempting to cut back your traffic.
Without having detailed insider knowledge of the carrier it is not possible to state for sure if what they are telling you is correct or not. As such any replies to you must cover all probabilities.
In summary it is possible that the carriers network does have some form of congestion but it is also possible that the carrier has commercial reasons for doing what they are doing.
To provide a more definitive answer would require the detailed traffic statistics and switch configuration information which is only available within the carrier. Without such information nobody can make a statement which supports or refutes the carriers claims of congestion.
You may want to ask the carrier questions such as:
Why is only 4 E1’s affecting the network?