Angel comes in many sizes, however the current sizes sold (therefore less likely to have gone off or be fake) are 15ml, 25ml, 50ml, 75ml and 100ml.
The 100ml and 75ml bottles are ALWAYS refillable. If you have purchased one that is not refillable, then consult the seller, and question HOW they obtained the bottle.
Some bottles are refillable, and some are not. If it's a non-refillable then when you take the lid off (which would only come off with substantial force) the silver cap will be crimped around the bottom. This means it will not come off.
However, if you have a refillable bottle, the lid/cap will come off much easier. NEVER twist the cap off as this will break it. Pull it directly away, using a cloth to protect the skin. The silver cap will twist off with a little force, and you can refill your bottle in a store or by purchasing a Flacon.
Genuine bottles should contain the appropriate sticker, shape, size and etchings. If all of this is absent, you are in possession of what is quite likely to be a fake.
If you buy a bottle online and it comes in a white, corrugated card box/sleeve this is NOT a resale item. These are only distributed to stores for use as a tester. Hence, the 100ml sizes, priced at £109 are unsurprisingly the most-faked or most-stolen and re-sold versions, owing to you believing you are buying a real bargain.
If you are ever unsure, it's best to buy directly from a store rather than risk your sense of trust on eBay. There are many genuine sellers, like myself, however there are many people ruining the level of trust by selling fakes, knock-offs and stolen versions.
As always, buyer beware.