Tourist Visa to Student Visa Rejection

I came to Australia in August 2022 with my family (Mrs. and 3 year old son) on visitor visa to meet my Brother in Perth. We liked the country and decided to apply for Student visa. My wife finished her BCA in 2016 and we met with an Immigration agent and he recommend us to get COE for Advance diploma of Business leadership management from GCA college Perth. We got the COE and applied for her student visa. Last week we received refusal and in the refusal letter Immigration officer indicates that we are failing to meet GTE requirements. Now our MARA is recommending us to apply for ATT and continue her studies. We are in dilemma should we trust same agent and should we seek help from other MARA. They are so many of them in this industry and don’t know whom we should trust. If someone have gone through same painful process can you please advice us what we should look for.

Thanks in advance for your advice.