As a consultant to the industry I have seen all manner of processes used to get calls to and from techs.
At the very least you should be looking to use email to communicate with the field. I suggest email over texting due to the character limits on texts. Plus email provides a better archive of the communications. Most of the major ERP systems for Dealers have this capability. There are also add-on packages that will provide even greater capabilities including allowing the techs to dispatch and close calls from the field. This will allow a single dispatcher to handle more techs as the need to communicate with them directly is greatly reduced. While you want to increase the dispatcher's ability to handle more techs you also do not want to put an undue administrative burden on the techs thereby limiting their ability to perform their principal function, servicing your customers. I would be happy to discuss this directly with you further if you would like.