I bought 88 dollar package of 4 tests for Advanced...

I bought 88 dollar package of 4 tests for Advanced Taxation, the explanation is generally fair but when I need them to go deeper on some answers that are not properly explained or explanation countering textbook, the academic refused and said can comment on if it's an error or not. So to get further explanation on the questions I purchased, I have been advised to purchase their tuition course which I'm not interested. And there are errors and spelling mistakes.