from the information that you provide I’d say it’s unlikely that 4 E1’s with the traffic load that you mention is causing “disequiibrium” and “considerable influence on other customers”. However it is not impossible.
From what you write (and from other postings on this site which appear to be about the same subject) there are several possible reasons for the EWSD operator to say what they have said. These being:
1) They have a serious capacity problem in terms of trunking and the traffic from the 4 E1’s is contributing to this problem. From the size of the network that you describe the traffic from the E1’s alone will not be the only cause of the capacity problems. It may be that the operator is attempting to reduce traffic from other sources also. If this is the case then the operator needs to upgrade their capacity. There may be certain reasons as to why they cannot/won’t upgrade their capacity.
2) The ISDN shelf/cabinet of the EWSD that the 4 E1’s are conncted to has an internal matrix that may have been sized to handle normal business traffic rather than carrier traffic and the traffic from the 4 E1’s is causing this matrix to become blocked. Are the majority of the 950’000 minutes from the 4 E1’s sent during the standard business hours of the country in which the operator is based (from you surname and the fact that the operator uses EWSD’s I’m guessing Armenia?)?
3) The operator may want to raise the rates that you are being charged and this may be a plan to ask for higher termination charges. Alternatively they may want to stop terminating traffic from smaller operators and only take in traffic from larger operators on C7/SS7 interconnects(I’m assuming that these 4 E1’s are used to terminate internationally originated traffic). If the traffic originated is national traffic then this may be an attempt to restrict competition or to ask for higher termination rates.
4) Some larger operators now have a company policy of only connecting to other operators with a minimum number of E1’s (often 10). It may be that this is the case here and the operator wants to stop dealing with an operator with only 4 E1’s. The companies that have taken such decisions believe that dealing with smaller operators is not cost effective for them.
Hope this helps.