I bought a sim card (data only) in Guadeloupe whil...

I bought a sim card (data only) in Guadeloupe while on holiday for 6 days. It came with 150mb of data. I recieved a sms stating I had been given an extra 100mb and I also purchased another 500mb. Within 3 days the data had run out although I was only checking emails and chatting a couple of times a day and my phone stated I had used only 142mb. On questioning this at the store I was told that the 500mb had been put on the wrong number (not my mistake) but there was nothing I could do about it. They could not explain why the data had run out at 142mb. I purchased a futher 500mb and that ran out in 2 days thought my phone stated 260mb used. At the store again it could not be explained and nothing could be done. The guy there informed me I had been sold a sim card that offered very bad value and should have been offered another one. I therefore spent 50 on almost nothing. What a discrace and terrible customer service from this company. I have complained via email but have had not answer.