What is your actual speedtest result?
I am using 250/25, but my phone can only reach speed averaging 40-70mbps.
If I used laptop, I can reach 240mbps.
I mainly download only from phone.
It is kinda a waste to upgrade to higher plan if your phone can't support it.
Update: my laptop is using wifi as well, and can reach almost 250mbps.
https://www.speedtest.net/result/11313914812
93/38 on a 100/40 plan on WiFi on a weekend afternoon. Pretty damn good.