There could be an intereference/congestion issue. What router are you using now?

Decent router for 3 floors will be Asus RT-AC86U, or mesh WiFi.

State your budget

since u no gip budget buy 2 units of below

tis wire LAN link mesh 2 each other
https://www.asus.com/my/Networking/RTAC68U/    or tis
future proof https://www.asus.com/my/Networking/RT-AC86U/

or tis wifi link mesh 2 each other
https://www.asus.com/my/Networking/RT-AC5300/

each floor 1 Wireless AP will do the job

Yes that is really old and not fit for use anymore, as it only supports up to 300Mbps and only N and its hardware is really insufficient. Time for you to upgrade to a much better router.

Don’t bother calling TM. Get a new router. I would recommend TP Link C7 v4, at the minimum, or the Asus RT-AC1300UHP.

You don’t have to replace the modem, just the router. Make sure you get the PPPoE username and password.

Are you still on contract? If you are not, try to go to TMpoint and renew your contract for a lower fee, and ask them to give you completely new equipment. Your equipment is all really old now.

Using Asus RT-AC68U in a 3 storey home, with no issue.

Router is located in the middle of the house (master bedroom).

You may need to test the best channel number to reduce congestion / interference from the neighbours ...

Just call 100 or TM live chat to know your PPPoE username and password.

They might or might not help you to replace it. You can ask them if they will replace your router, modem, and UnifTV decoder. You would do better to go to a TMpoint to negotiate with them. See if they can give you a better price for your current Unifi, and if all the equipment can be changed if you resign contract with them.

Otherwise, just change the router and you will be fine.

Using mainly 2.4GHz on 20Mhz channel bandwidth. This is more than sufficient for 50Mbps Unifi speed.

On 5GHz, the signal will be weaker but is usually enough to reach the upper floors.

Yes, that is the best they can provide, for now, so it is up to you.

you can get better comments if y describe this house - sg ft per floor, where will u use devices, where u will place the router, etc.

3 levels... typically hard to do with just one router for wifi.

rm700 won't get u much; a super duper router that MAY do for u will cost 2-3 times that.

yr case is not new, many have posted, a lot of comments/suggestion given in many threads.

but i have yet to read one such case where the solution is affordable, simple and TS satisfied.

TS, for new house just register new line and you'll get brand new Unifi equipment. Most likely you'll face different issues in your new house with the new layout..

u definitely can try the stock router they will give u when upgraded to 100 or higher.
but it is a fact wifi will not be good enough for even a std 2-storey house.

assuming a footprint of 1,000 sqft x 3 floors and router is at grd (level 1), it will ok for level 2 (except the far corners) but level 3 will be tough.
that is assuming u get a better router - the stock router won't do well even for level 2.
if u want level 3 coverage, either u use another router on level 2 as wifi extender which sucks becos 1/2 is already lost.
the best way is to lay a lan cable from router at grd level 1 to another router at level 2 or 3 to serve as access point (ap) for levels 2, 3.
this is a bit of trouble, but perhaps possible for yr new house under renovation?
also, try to get 100mbps at least to cope with the losses in yr tall house.
lastly, consider yr devices... old devices using in 2.4ghz will hv more difficulty; newer running on 5ghz can receive wifi better.

all that is said has been said many times over but there is no pinned thread for u to read.
i collected those threads and have added yr thread too!
you can see the discussion is repeated over and over:

Is it my router's problem ? (Tech Support)
https://forum.lowyat.net/topic/4618409/+20
Router sucks at wifi,homeplug any good?
https://forum.lowyat.net/topic/4594095/+20
Unifi standard download speed for 100mb
https://forum.lowyat.net/topic/4551990
2.4Ghz and 5Ghz connection, at different speed
https://forum.lowyat.net/topic/4195926
Need some advice on extending internet coverage, Condo,<2,000SqFt, thick walls
https://forum.lowyat.net/topic/4549805
Router replacement for unifi 100mbps, Router replacement
https://forum.lowyat.net/topic/4548858
Router recommendation, Need high gain and stable
https://forum.lowyat.net/topic/4538857
Best router for Maxis Fibre 30mbps, Best router for Maxis Fibre 30mbps (Home Networking)
https://forum.lowyat.net/topic/4547385
Router Recommendation
https://forum.lowyat.net/topic/4519582
wta unifi wifi extend, suggestion (Unifi)

I think better before u go into new house you lay LAN cable around the house as 50mbps will be upgraded to 500mbps for utilizing all speed and add the cheap ac router as access point

not a router expert but i wud think yes - best router as main... connect 2 others via lan as AP's.

Yes. That would work, but the APs can’t be average if you want full speed, they will need to be good and your router will need to be one of the top ones.

Yes - but 5GHz is much less congested.  You may need to use a WiFi analyzer app for your phone and see which channel is the least congested out there

https://play.google.com/store/apps/details?...alyzer&hl=en_US