@MitchDugg This a reply I sent to a similar query.
Next time your speed drops reboot the modem and see if the speed picks up.
My speed went way south suddenly for no reason. It happened on a Weekend , I would reboot the Modem and it would pick up for an hour or so then die again. Repeated this several times over the weekend, it was bad weather so I was streaming and not very happy.
On the Monday after work I rang Optus Service and was lucky enough to get through to an Optus Representative who listened to the symptoms and what I had done to fix the issue.
I assumed he must have called my account and checked some things and then he told me he was going to disconnect me from the Tower, he asked me to hold the line in about 20 minutes he came back and said it should be fixed. I explained to him I was not at home and he said to me when I get home reboot the modem, which I did and it has been fine since.
I asked him was the procedure he performed a High Level Rebuild on my Account and he replied why do you want to know? I said that if the issue is not fixed and I need to contact support again re the issue I can say I have already had a High Level Rebuild on the account, He replied it was. I believe a High Level Rebuild maybe also known as Resetting the Codes on your account. Service has been fine since.
Just a couple of things you can do at your end if possible position the Modem facing the tower near a window. If unsure where your closest tower is go to rfnsa.com.au, enter your postcode and use the filters on the side to narrow the search to Optus, 4G & 4G+.
If you have 4G 700MHz, 1800MHz, 2100MHz 2600MHz and or 4G+ 2300MHz or a combination of these log into the Huawei Modem Click on Network Settings, Mobile Network, Mobile Network Searching and Preferred Network Searching and from the Drop down menu select 4G only. Click save and see if the connection is any better. You could try the other 4G options from that menu to see what gives the best result.
Once you locate the closest tower positon the modem as best you can. If the closest tower is 5G active but you cannot get 5G you can use the Optus @home app to optimally position your B818.
Just have your 4G Phone Internet Connection active, Location Services active, do not worry about the No WiFi connection error, there is a White Speech Box with a down Arrow at top Right of the page click on the box and Optus 5G support.
Scroll through the various pages, do the compass align action input your address and once your get the best alignment possible rotate your B818 to match.
I also use a B818. Speeds were 80-100 down 20 up. This week they fell to 0.2-0.8. All 4 family 4g phones experience the same loss of speeds. 3 calls to Optus techs and all have different stories. Research suggests that because up load speeds are not slowed the issue is Tower Congestion, I assume due to the Virus. This would be understandable if Optus would admit this to be the case, but as Tower Congestion is a valid reason for terminating a contract: they will not, even so far as to say they do not keep traffic records, which by law, they do.
The bigger problem is that they appear to be throttling certain towers at certain times.
As Optus seem to cloak Tower Congestion in a cloak of secrecy, the only option is to approach the ombudsman, which is an easy online process.
Do you know which tower you are connected to?
Optus tech last night told me the average download speed for a faulty tower my wireless broadband AC800S connects to is, so they do have access to speed info.
Optus tech support is not very good at giving straight answer or even correct answers when you have issues with a faulty tower.
Tech support will waste allot of time going over the same thing when you use myapp to get a status updatae on an problem report as they will NOT read the PR when you ask and then after they have tried various things where you keep saying its a tower fault look at the PR they will finally read the PR and say that there is a tower fault.... doh doh doh.
If you get the run around make a formal complaint that the service you purchased is not as expected and what you want done about it.