The whole process give me a headach

I have been a customer of TM for almost 20 years.  The process of working with TM goes from great and then to giving me a headache and back and forth from these to extremes.  When it hits the headache stage, TM loses a sale.  (A few times have come close to leaving and sometimes I with I had.)  Recently, I tried to upgrade my S24 using my computer and not the app.  I walked through the process.  During the process, it says my new payment will be $17.99 a month.   When I get to the end of the process, it says my new payment of almost $39.00 a month.  I called support and they tried to help and to explain – another headache.  They sent me a link so they could see what I was doing on my phone.  I don’t like using my phone but I tried.  While using the app on my phone it kept trying to setup a new phone number.  I asked the representative if they could just take my order over the phone and was told they could not.  I don’t understand so I simply gave up.  TM loses money again.  Upgrading should be very, very simple but once again, TM has gone above and beyond to make it difficult and,  also, how I feel, add false advertising to confuse the client and trick them into a higher payment.