Sky 500 broadband problems

[Centurion_1]

I've had full fibre fitted on 9th June with above contract. 
I have an iPhone where the speed test she's 500mps but the android work phone only shows 40mps on speed test and keeps dropping out. Why the difference on phones? 
Plus my ring doorbell shows very poor connection yet my tv and Alexa works fine and I only live in small 2 bed flat so surely 500 should work fine all over. 
Openreavh have been back out to test everything and said it's the router. Sky have sent out another router and still the same problem. 

Any ideas?  Must admit I'm considering cancelling as still in cooling off period as never had this problem with three mobile internet 

[Chrisee]

@Centurion_1 the speed a phone will connect at depends on the WiFi speed where the phone is located and the ability of the phone. The same applies to your doorbell. Poor WiFi coverage is probably the most common question we get in the forum. In many homes a single Sky hub cannot provide a usable wifi signal in every room due to the layout and type of construction of the property especially in older homes. Assuming the hub is in the best possible position which is out in the open on a surfsce then the only answer is additional wifi sources. 

Your choice.is to either buy Sky's add-on WiFi Max bundle which can supply up to 3 extenders see https://www.sky.com/help/articles/sky-wifi-max or buy your own wifi system and use that instead of the Sky hub's WiFi.