PIP telephone assesment

I was sectioned in december 20, had to complete a review in march 2022. My mental health worker wrote a very good supporting letter for me. She asked them if they need any further information to get intouch with her. Also that she would prefer me not to have a medical assesment as it would effect my already fragile state, and that it could excacerbate my mental health.
I was diagnosed with Bipolar, I have always suffered with depression but they have always disregarded that because I didnt have any mental Health input. Also I do have Fibromyalgia, Menieres and severe arthritis of my knees and hearing loss.
Anyway I have been booked in to have a telephone assesment next week. I called IAS, to ask why I needed to have a medical, he looked at my evidence and said that they didn't have the letter from MH.
I also asked to have the assesment recorded but was told that I need to do it myself. Is that correct? Also I've got a samsung s9 galaxy phone, I cannot see how I can record the calls myself. Are there any recomendations for apps that do this?
I did think that maybe I should have an assesment any way as mental health social worker doesn't really know how my physical health impacts me. Have I made the right decision? Just looking for a little bit of advice, many thanks

Thanks Gary for your response. He couldn't find the letter but said I could ask them if they could call her. I have messaged her but she hasn't responded to me, so could be on holiday as another Mental Health Social worker saw me just recently, and she doesn't seem to be online either. I didn't think to ask to send it to them. No the letter did not state OPD but did cover all of the descriptors rather well. I have more evidence to add also as I sent my review back March 2022. If I need to do a mandatory I will send in additional evidence. Hopefully DWP have my letter!

I telephoned IAS yesterday and would you beleive it they have the letter, but said that because it was from march 22, it wasn't really evidence they would consider as it is out of date! Managed to get hold of my social worker and she is going to come to my house when I have the telephone assesment. It isn't my fault that pip have taken over a year to do an assesment. They said even though the letter stated for me not to have assesment they needed to carry one out as pip had decided I needed one. Thanks for your help, will let you know how it goes when I receive my news

Just to let you know I had my assesment on 12th May, I had my support worker present too. The assesment lasted 1.5 hours! I recorded it myself on my phone she was unaware, but didn't ask me about that. She was trying to catch me out all through the assesment and anything that was said, she twisted it to not award me points.
I received a text from DWP in the afternoon to say that they had received the report, and not to get intouch unless my circumstances change, and should hear within 6 weeks.
I telephoned pip got cut off twice, but third time lucky! Was on hold for an hour and 15 mins. Anyway was very pleasant with the call handler and requested my pa4. She looked to see if they had it, which they did, so she posted it on the same day. Told could take between 10 and 14 days. Received it on thursday, so not that long to wait. Luckily even though report is contradictory in places and she was trying her best not to give me points, I managed to score 12 for care and 14 for mobility. She recommended that I'm reviewed again in 18 months, so even a shorter period than previous assesments. Have been ill since 2011, and have many health problems that will not get better, I wish they would. She beleives so!
Do decision makers stick with her points as she did not take into account any medical notes at all, even though I sent in a big bundle? Hopefully so, but not if they follow her 18 months recommendation! can I take that to mandatory if needed, as my support worker said I should not be assesed as much as I am as my conditions are not going to get any better. Fibromyalgia, Carpal Tunnel, Hypoithroidism, Menieres, arthritis in hips and knees, will need knee replacement, and then diagnosed with bipolar, although I have always had depression and anxiety, that was never taken notice off as didn't have CMHT support even though I had been referred to Enhanced mental health and had cognitive behaviour therapy, that did not work at all for me. Also crisis team have said in a letter that I have PTSD.
Thank you to all the team that work in Benefits and Work for all your contributions and helping us the claimants to learn more about the process, many thanks