Step by Step Instructions for iCall

there are other less safe and even less supportable methods, but the intended method of integration between iRules and iCall is to use the iStats commands in an iRule.

For iCall specifically, this article puts all the pieces together well but does not address the need for an iRule integration.

For that, this article should bring clarity. Note the troubleshooting commands/log status at the bottom that will help while you are developing your solution.