Shipexec is not able to handle multiple requests from OTM through OIC during rate call

We are integrating OTM with Shipexec to get parcel carrier rates. 

As Shipexec is not an OOB integration with OTM, we have created an OIC integration (which is configured as an External rating system) to get the rates from ShipExec. 

When we do a rate inquiry from OTM or plan an Order with no constraints , OTM sends one request per active rate service available in OTM to OIC and OTM gets the rates from ShipExec and response back for the service. We are having 20 plus active rate services and this creates 20 different calls to OIC and in turn to ShipExec for each inquiry or order.