Buying more data

I was told I had run out of data on my plan and sent a link to buy more I bought £10 of data but couldn’t access the internet so phoned Lebara to be told the £10 was used to pay towards £93 of data I had used ?? The customer service agent English wasn’t very good and he didn’t explain where this £93 had come from as I didn’t have any data to use !!

Strange I paid £5 to top up my data , and still had none . I probably shall be cancelling my account .