"I had accepted the claimant commitment when doing my form. This extra letter for an additional claimant commitment via phone or in person is what is confusing me."
I think people need to be aware there's a bug in the DWP computer system where many people who get both Contributory and Income related ESA will receive letters from the DWP saying just "You are entitled to Income-related ESA.." with no mention of Contributory, giving them the false impression they aren't receiving contributory ESA. Two ways to check are:-
1. Was one ESA payment £10 higher than usual in December, and
2. Do you receive an annual P60U from the DWP showing a PAYE reference as "ESA500" (even if you don't pay tax on it due to being well below the annual threshold).
^ If so, then you do get contributory ESA (because only that is taxable and gives the £10 Xmas bonus), and Mumbo_Jumbo's two claimant commitments are probably one for UC and another for New Style ESA.