I entered the wrong phone number in WhatsApp and now, it is no longer the same as the phone number on my phone

My question : 

Situation: I bought a new iPhone 13, & gave my old iPhone X Max to my husband.  I then put my old SIM in the iPhone 13 and set up his phone with a new SIM. Everything worked except….

Problem: as I was setting up two similar phones simultaneously, I stupidly used Change Number and entered the wrong number, (ie my husband’s) in Whatsapp on my new iPhone.

Now, my new iPhone 13  has the correct phone number (ie my usual number), receives SMS, calls etc correctly. The problem is that I can’t receive any WhatsApp messages on my new phone because the phone number in WhatsApp is not mine! It is that of my husband! 

He can’t use What’sApp to message me as the number associated with his WhatsApp is my number! 

I want to change that to his number (without erasing my chat history).

WhatsApp maintains in the Change Number area that one “can’t undo this change” . 

Another related problem:  Chat history: I would dearly like to keep it! (At the moment, it is intact on both phones and is backed up on iCloud)

I tried on 5 occasions to get help from WhatsApp and they never once addressed the issue at hand — just sent me extraneous information on how to change number or move groups etc. 

There is no error with my iCloud account on either of the two phones! On iCloud, my contact information is all correct — phone number, email etc.

Both phones are using iOS 15.2.

Question: 

a) Despite WhatsApp’s warning,  can I use  Change Number in WhatsApp to revert back to my correct phone number —- the same one as the phone, and the one I used to set up WhatsApp years ago? Or,

b) Should I delete the WhatsApp app and redownload it and then enter my correct phone number?

If I can’t revert WhatsApp to my previous (and present phone number), then, I can’t use WhatsApp again at all. I must have a WhatsApp that shows the same number as my phone! Or, 

c) Are there other options? 

Please help me with this problem as Apple Stores no longer offer much assistance (Covid) and WhatsApp is not really supported by Apple.

Please give me a step by step answer as I can’t cope with more problems. 

Thanking you in advance for your precious assistance (as this is poisoning my life at the moment!)