Anyone tried or interested in this type of electrotherapy might like to read the 2015 article by Pr T Watson on this page entitled "Interferential Therapy" It includes contraindications and a list of references but looks as though there are no published studies for pelvic or abdominal pain.
It is generally osteopaths who use this form of therapy in the UK. It would be interesting to hear from those with pelvic pain who have tried this.