@Brandy-R 

Strange...

Be sure your router has up to date firmware as there are Tether and configuration corrections.

See https://www.tp-link.com/us/support/download/archer-ax50/#Firmware

I would be concerned that the router may have been hacked. If it were me, I would close that Tether account, not use it, and have support remove any link to my router, update the firmware, do a factory reset, then set the router so only my connected PCs can change the settings if the option is available. IMHO, I feel the limited capabilities of the Tether app is not worth the security risk nor any routers that require you to use some on-line portal to control your router. 

@Brandy-R 

If you bound the Archer AX50 to your TP-Link ID. I would recommend changing your account password.

Here is a link that shows how: https://www.tp-link.com/us/support/faq/1442/

Additionally, I would change the local password as well (Advanced > System Tools > Administration).

@ArcherC8 

My firmware is updated and I think you're right. We previously had everything hacked and when I say everything I mean everything. Computer then my phone (linked to computer) and our gateway. I would change our gateway password the next day I was locked out. It was horrible. 
So I got a new phone, bought a separate modem and router and never hooked up my computer. Well the guy we hired to install everything looked at my husband's computer and said "it didn't looked infected " (I think it was), and now we're back to this. I did a speed test and was only getting speeds of 35.4 and a notice of unstable connection. I can't get into the modem advanced settings even after resetting it. I called our internet provider and set up a service call, But trying to figure out if it's our equipment issue or internet connection issue. 
I appreciate your feedback and for not making feel stupid for my question. 

@Brandy-R 

Some other things to do if possible:

• Do a factory reset.
• Be sure to change the SSIDs and passwords.
• Use the highest WIFI security you can
• Use the white list function to allow only your devices to access the router.
• Limit setting router changes to specific PCs.
• Turn off WPS.
• Use firewall
• Avoid UPnP
• Do not use Alexa.
• Turn off ALG setting that are not used.
• May want to turn off the modem and router when not in use ie at night, when not at home,...
• Avoid opening any ports.
• Back up, and then reinstall the operating systems on your PCs. Add files back as needed (not programs)
• Use good quality security software
• Get apps/programs from the original source, not any third party links.
• Do not open email that you do not know the sender (even then it is not guarantee)
• Do not use email links. Go to the original source.
• If you have an old router, set it up with the old SSID and password, but do not attach it to the modem. See if it gets infected/changed as they may be using WIFI to get in.
• If in a multi-dwelling (apartment), be sure where all your cables go. 
• A VPN may help.
• Use the traffic monitor to see if you can identify bad activity.

@ArcherC8 

You sound like a technician. If you are I'd like to ask you a couple more things. And answer your questions 

I have a new modem Arris surfboard SB8200 and Archer AX50 router. We hired someone to set it all up after we were hacked and I think maybe he didn't do a very good job. 
Today I received an email and a phone call from someone saying he was from Comcast responding to my recent billing inquiry. He had all the information correct, but something about his thick Indian accent and his name Bob on my voicemail didn't sound right. So I tried to respond to his email and sure enough it was undeliverable. I immediately called Comcast and they verified he was not from Comcast. So now my problem is trying to figure what of my accounts are comprised. Because this guy even had my husband's phone number. So he must have been in my account. We were hacked so bad before I was in tears trying to sort it all out. I have no idea where to start this time. 

@Brandy-R 

Check this site to see what you can do to best secure your router.

https://routersecurity.org/index.php

I suggest you ensure you have the latest firmware and then reset it to factory settings then make the router's changes. In most cases the two router options, is not needed as the other steps should be fine except against the most skilled and determined bad actors.

I do recommend using the options to limit devices by MAC address. That is where you need to enter into a whitelist every device's MAC address which must be in the list for the device to sign on to the router. Many devices have the MAC address printed on a label on the device or on some you need to sign on to the device to find it such as iPads and phones.

If you were hacked, it may have been by means other than the router. Each device needs to be reviewed and correction made.