Unfriendly service

We were at Doppio Zero on the 22nd & 24th of March. On both occasions we found the waiters to be very unfriendly. Not sure of the names but if memory serves me right a man called Joe?? and a lady called Melody?? Especially when it comes to paying and leaving at least 10% as a tip, one is not thanked nor is there a friendly goodbye We were in the company of overseas visitors and felt quite embarrassed by the lack of polite and friendly service. Nobody came to the table to ask if all was well once the meal was served. A lot of staff training is needed. Some of your waiters are clearly NOT an asset to your business and are doing more harm than good. I will be visiting again, and will no longer leave any tip at all for poor and/or unfriendly service