Why can't interlocutors on some numbers hear me through IP-telephony?

Question

Asterisk

Our organization has ip-telephony with the ability to call external numbers. The problem is that when calling externally, there are no problems with most numbers, but there are numbers on which we are not consistently heard, but we hear them. If there were problems with the configuration on our side, absolutely everyone would not hear us. (Or am I not understanding something?) I contacted the telecom operator with a question, technical support says that everything is fine with them.
UPD: From communication with the operator's specialist, it turned out that this was somehow connected with tone dialing. All the numbers that can't be heard are served by a station that doesn't use tone mode or something like that. Allegedly, we have some kind of setting on the PBX that requires tone dialing and nothing else.

Answer 1

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