Three

Summary based on one visit to get a SIM while on holiday:
–Cheapo phone/​unlimited data plan for £15 (airport £20)
–friendly, helpful service
–no waiting on my visit

Really, this review can only be expressed by recounting the conversation:
Laura: Hi, I’d like to top up my portable broadband dongle.
Staff Member: Why are you here, then?
Laura: Um, because I’d like to… top up… my dongle?
Staff Member: You can’t do that here, you can only do it online.
Laura: That’s strange, I know I’ve topped up at a 3-​store before…
Staff Member: Like I said, you can’t do that here, sorry.
Laura: In the past I’ve received a print out with numbers on it that gives me more credit, like some sort of voucher?
Staff Member: So you’d like to buy a voucher then?
Laura: Does the voucher allow me to top up my dongle?
Staff Member: Yes.
(Commence stare down that went on for unidentifiable amount of time…)
Laura: Ok… I’d like to buy a… voucher. (Pulling out American Express card)
Staff Member: No. We don’t take Amex.
Laura: Er… I know I’ve used my Amex at another 3-​store?
Staff Member: That’s why we have that helpful sticker on the door with the little credit card logos. See? No Amex logo.
He then — wait for it — walked away from the till. Yes, really. And I then chose to take my business elsewhere.
But not before overhearing the beginning of yet another stellar customer service experience:
New customer: What? But I paid with my AMEX here just last week…
Staff Member: See the little credit card logos on the door…