CP05 Notice + IRS Letter About Phantom Amended Return - $5,000 Frivolous Filing Penalty Waived for Return I Never Filed - No Refund Movement Since February

Just got a CP05 letter saying I need to wait 120 days for my refund while they verify my wages. Has anyone gotten this? My transcripts show no movement since February and I'm really getting worried about my refund. Starting to feel hopeless about this whole thing. Today I received another letter from the IRS dated May 03, 2024, in response to something I supposedly submitted on May 02, 2024. The letter states word for word: "Dear Taxpayer: Thank you for your response of May 02, 2024. We're sending your response, dated May 02, 2024, to the office at the address at the end of this letter because: Your amended return corrected your frivolous position; therefore, will not be assessed the $6,000.00 frivolous filing penalty. However, your amended return included other changes which require further examination. You will be contacted if additional information is needed to process your case. Find tax forms or publications by visiting IRS.gov/forms or calling 800-TAX-FORM (800-829-3676). If you have questions, you can call 866-883-0235. If you prefer, you can write to the address at the top of the first page of this letter. When you write, include a copy of this letter, and write your telephone number and the hours we can reach you. Keep a copy of this letter for your records. Thank you for your cooperation." I'm completely confused because I never filed an amended return or had any "frivolous position" that needed correcting. I just filed my regular taxes and was expecting my refund. Now I have both the CP05 saying to wait 120 days AND this new letter talking about amended returns and penalties that I don't understand. The letter mentions a $6,000.00 frivolous filing penalty that they're not assessing me, but I never filed anything frivolous! It also says my "amended return included other changes which require further examination" but I never submitted an amended return at all. Has anyone dealt with this combination of issues before? I'm completely lost and feeling even more hopeless about ever seeing my refund. My transcripts still show absolutely no movement since February. Should I call the number they provided (866-883-0235)? Or should I write to them as suggested in the letter? I'm worried if I contact them it might delay things further, but I also want to clear up whatever confusion is happening here.