O2

Hello all I'm just wondering if someone can help me my my pohne won't let me call any one or text anymore or I can't used my mobile date I pay my bill and I got unlimited calls and texts and 60g of date left just wondering what can I do please

I had no mobile date or can't make no calls or test I'm on monthly contract I paid my bills I can't get hold off o2 I had this for 2 days now