iPhone 15 Pro Max - Charging the Battery

This is my first smartphone and it takes over an hour (often and hour and 15 minutes) to go from 66 to 100 and from 70 to 100, etc. This has been the case since the first day of purchase but I assumed that this was the way that all smartphones are. I have never dropped the phone and I keep it far away from any food/beverages/liquids. I have talked with several Reps and they are each very thorough, polite and professional. I've been told that it may be best to bring it into the store as they were unable to locate any problem via diagnostics. Yesterday I called in to ask if it is worthwhile for me to struggle to get to the store if they might send it out regardless (I was trying to minimize the possibility of additional issues because I'm sure that packages are handled a bit roughly by Fedex/Ups/USPS.) That Rep advised me that there is nothing wrong with my phone and that the iPhone 15 has a very large battery and this is why it takes longer to charge. I explained that I'm scared because if I run out of charge I will not be able to contact my transportation and vice versa (I have multiple disabilities.) I explained that I purchased a battery pack but if I run out of charge it will take at least 15 minutes to just get it to 10 (if I am lucky.) The Rep told me that I might want to consider purchasing a back up phone such as a "Burner." He also advised that going to the store will serve no purpose because there is nothing showing as a problem on the phone and that they will not be able to do anything for me. I had purchased Apple Care+, I do not know if this makes any difference. I do not know what to do, should I go back to my old flip phone and use this phone as a music player? I cannot afford two phones.