[bilky asko]

Probably but I wouldn't have thought they'd have the ability to change the message you hear so once you've gone past 20 votes, they just don't count any more votes that your phone number has made.

The 20 vote limit on all forms of voting has existed for years and they've certainly mentioned it on the show previously, I remember Alesha saying it last year for example. It's listed in the terms and conditions here: eurovision.tv 

The BBC Ts&Cs specifically state that the limit only applies through the app, and they supersede anything the Eurovision site says. This was also the case in previous years.