（レストランやカフェで店員さんを呼ぶ時の）すみませんって英語でなんて言うの？

You must attract the waiter's attention or ask someone to help.

Excuse me is a polite way to ask for assistance from someone.

Sometimes instead of just saying "Hi" I say "Hi there" so that I can get a specific person's attention. Or saying "Hi there, excuse me" usually alerts the waiter that you are trying to get someone's attention rather than just speaking to someone else.

Hello! - to grab the servers attention, normally they should come straight over apologize and answer your request. Excuse me, we have been waiting! - This will tell the servers that you are not impressed, and psychology tell them to look after you better. I would only use this if the waiting time has been unreasonable. Can we have the bill please? Can you take our order please? If a server is walking past and you manage to stop them this is the best thing to say.

example "excuse me". or "excuse me waiter". or "excuse me waitress". In a restaurant or cafe the term waiter or waitress is used. If you are in a store or shop the term would be assistant. Then you can just say "excuse me please".

If you would like to call a waiter or waitress, your communication will be short and loud enough to hear from wherever you are seated or standing. Make sure to have eye contact or a hand lightly raised. Assistance: help, "Hi there, please get me another glass of water with ice."

Excuse me (their name here).'' can be used to call your server over to you.

"Excuse me" is a causal term used in many contexts, in this context you can use it to get someones attention, for example in a restaurant or bar, to summon/call a waiter over you are able to say 'excuse me' as it is a polite expression of getting someones attention, also you can use 'Hello' to get someones attention.