calling him "Uncle" shouldn't be offensive at all since he was anyway quite elderly for us.

Calling the waiter uncle might have offended him because, possibly he thought that you either mistook his age by his look or he probably just didn't want to be called as such.

Is this correct or we were wrong in thinking so?

I'd say neither party is wrong. You called him uncle as he appeared quite elder than you and he got offended for possible reasons I mentioned above.

How should one address servicemen/servicewomen in the restaurant in a proper way?

Once I went to a restaurant with my friends and one of them called waiter uncle. Though he didn't say anything at that time, but it appeared that he got offended. So I started to call him sir and he was happy to be called as such. I only did this to show him some respect, but you don't have to call a waiter sir/ma'am. You can, but it's not necessary.

You can try following approaches without offending anybody.

1. Whenever you have to call a waiter, say Excuse me.
2. If this doesn't work, say the same and raise your hand.
3. You can ask him/her his/her name and the next time, you can call them by their name.

calling him "Uncle" shouldn't be offensive at all since he was anyway quite elderly for us.

Calling the waiter uncle might have offended him because, possibly he thought that you either mistook his age by his look or he probably just didn't want to be called as such.

Is this correct or we were wrong in thinking so?

I'd say neither party is wrong. You called him uncle as he appeared quite elder than you and he got offended for possible reasons I mentioned above.

How should one address servicemen/servicewomen in the restaurant in a proper way?

I am from India and at one time, I went to a local restaurant with my friends and one of them called waiter uncle. Though he didn't say anything at that time, but it appeared that he got offended. So I started to call him sir and he was happy to be called as such. I only did this to show him some respect, but you don't have to call a waiter sir/ma'am. You can, but it's not necessary.

You can try following approaches without offending anybody.

1. Whenever you have to call a waiter, say Excuse me.
2. If this doesn't work, say the same and raise your hand.
3. You can ask him/her his/her name and the next time, you can call them by their name.

calling him "Uncle" shouldn't be offensive at all since he was anyway quite elderly for us.

Calling the waiter uncle might have offended him because, possibly he thought that you either mistook his age by his look or he probably just didn't want to be called as such.

Is this correct or we were wrong in thinking so?

I'd say neither party is wrong. You called him uncle as he appeared quite elder than you and he got offended for possible reasons I mentioned above.

How should one address servicemen/servicewomen in the restaurant in a proper way?

Once I went to a restaurant with my friends and one of them called waiter uncle. Though he didn't say anything at that time, but it appeared that he got offended. So I started to call him sir and he was happy to be called as such. I only did this to show him some respect, but you don't have to call a waiter sir/ma'am.

You can try following approaches without offending anybody.

1. Whenever you have to call a waiter, say Excuse me.
2. If this doesn't work, say the same by raising your hand.
3. You can ask him/her his/her name and the next time, you can call them by their name.

calling him "Uncle" shouldn't be offensive at all since he was anyway quite elderly for us.

Calling the waiter uncle might have offended him because, possibly he thought that you either mistook his age by his look or he probably just didn't want to be called as such.

Is this correct or we were wrong in thinking so?

I'd say neither party is wrong. You called him uncle as he appeared quite elder than you and he got offended for possible reasons I mentioned above.

How should one address servicemen/servicewomen in the restaurant in a proper way?

Once I went to a restaurant with my friends and one of them called waiter uncle. Though he didn't say anything at that time, but it appeared that he got offended. So I started to call him sir and he was happy to be called as such. I only did this to show him some respect, but you don't have to call a waiter sir/ma'am. You can, but it's not necessary.

You can try following approaches without offending anybody.

1. Whenever you have to call a waiter, say Excuse me.
2. If this doesn't work, say the same and raise your hand.
3. You can ask him/her his/her name and the next time, you can call them by their name.