@Razor1979 

One feature that might be having some issues with this feature on your phone is fast roam.  We would recommend turnning off this feature in the router and then testing the call to see if its still dropping.  Fast Roam is desgined to make transistion from node to node more seamless but it has been known to cause issues with device features in the past.  If after turning fast roam off you don't see an improvement let us know.  we will need to know a few things though

1.  How many Deco units do you have?

2.  What hardware version are they?

3.  What firmware are you currently on?

4.  Have you attempted to switch the position of the units around?  Basically making the satalite the base and the base the satalite.

Thank you

@Razor1979 

Hardware version should be on the label on the bottem of each node.  As an example look at the 1st two pictures in this FAQ https://www.tp-link.com/us/support/faq/2053/.  Next to the serial or S/N you will see the Hardware version number.  usually listed as (US/x.x) or (Vx)

@Razor1979 

Models are regionally based as are the frimware.  The main difference is how WiFi is regulated different in the EU as compared to the US.  Certain frequency and channels are approve in one place and not in the other.  I see though that you are actually posting from GB region or the UK.  What I will do is tranfer your thread to our Global community who handles the UK among other regions.  A direct link to this community is community.tp-link.com/en.  Your post will be in the same category and have the same title.  Users and admins more familar with your region should be able to provide greater support than we in the US can.