Mario,
You should be able to tell via helm ls which may show you installed versions of Istio. These can be removed with helm delete --purge. It sounds like this gear is shared - I’d urge caution and seek out the individual(s) that are sharing the cluster with you that installed Istio to begin with to sort out your environment.
If you have a choice, I’d recommend using the template+kubectl installation methods. We document the helm methods for completeness, however, helm template and kubectl apply offer better reliability.
Cheers
-steve