Bad news about ISG behavior. I would call them – emails are easy to ignore or go into junk. The fault may be with your provider college/program provider. They should get their accreditation removed.
With regards to WSET and CMS. The Court inthe UK tend to recomend that you do WSET level 3 (or equivilent) before you attempt the Certified Sommelier exam. The CMS don’t run courses per se until you get to Advanced level. They also expect you to have at least 3 years wine service experience minimum. WSET and CMS were originally set up be some of the same organisations with WSET focusing on the wine trade and CMS to examine and certify wine hospitality professionals