FNB EMBARRASSMENT

I am very nervous about using my FNB credit card overseas as I am not convinced that it is well monitored. A few years ago I used my card to buy several items successfully. On the last night I took my hosts to dinner to thank them and to my embarrassment my card was declined. ***** suspected. I thought well an error occurred. The last time I went overseas again I was allowed to buy several items and again when I took my hosts to dinner the card was declined. ***** suspected. My question is if it was ***** why did allow several items to be purchased on my account or do they only monitor restaurants. I have learnt my lesson and will not use my FNB card overseas in future.