It seems that using the following karate-gatling dependency (version 1.0.1)

<dependency>
    <groupId>com.intuit.karate</groupId>
    <artifactId>karate-gatling</artifactId>
    <version>${karate.version}</version>
    <scope>test</scope>
</dependency>

the request are not passed as it is but there's an empty attribute (xmlns) added the the soap request, making my tests failing. That is instead of:
<service>123456789</service>
the request sent is having an empty xmlns attribute:
<service xmlns="">123456789</service>

The problem is quite similar to the one reported in https://stackoverflow.com/questions/57042497/karate-xml-element-changed-to-have-empty-namespace/57042773.
In this case it must be something regarding the xml libraries handled by karate-gatling. With the version 0.96 of Karate (and the equivalent version for karate-gatling) it worked fine.
As attachment the code for replicating the problem, with a README. You have to run it without the dependency and check that it passes. Then decomment the dependency in the pom to see that it fails.

myproject.zip