AT&T misleading online chat agent, and all department said they are not responsible for it.

I had at&t prepaid for over 3 years with currently 5 lines. and last week, I want to switch to at&t unlimited postpaid plan. So I start a online chat with an agent. I asked what should I do to transfer my 5 lines of prepaid numbers to postpaid. He told me just go ahead to order 5 new lines with new numbers. He said the new numbers would be temporary and my old numbers from prepaid will automatically port in to replace the temporary numbers. So I go ahead odered 5 lines online with the agent's help. I received sim cards yesterday but I found that my numbers have not yet been transferred. So I tried called at&t prepaid department, they said I need to do it in store only. Then I went to store. The store said that they can transfer prepaid number to postpaid directly but they can't port in the number to replace a exist postpaid number. And the only way I was told is to cancel my new ordered 5 lines and re-do the transfer in store. So the online chat agent totally mislead me!!! Then I go ahead call to cancel it today. the loyalty department said I was need to charge for one billing cycle because yesterday 12/2/2019 is the start of billing cycle. Then I'm really angry that I ordered these numbers because of mislead from at&t, and I need to pay for more than $200 to cancel them when I never use these numbers. It is rediculous that at&t just lied to me and put all the penalty to myself. I called almost all day today to different departments --- postpaid department, prepaid department, online department, fraud department. no one give the responsible for that. It feels that at&t's customer service is junk. 

Does anyone who know how to deal with this case?

Regards