i forgot to add that bill a) does not include gas usage although I am not certain why

Bill a) paid £76.00 by DD .Total charges £106.32 DR. Outstanding balance £30.32 DR. Electricity units 768Kwh @ 11.007p per Kwh Bill b) paid £695 CR by DD.Total charges £493.50DR + £30.32 carried forward from bill (a. Outstanding balance £171.18 CR.Electricity units 1750Kwh @ 11.007p per Kwh.Gas units 6253.2 @ 3.075 p per Kwh Bill c) paid £695 CR by DD..Total charges £599.82 ( nothing carried forward) Outstanding balance £95.18CR Electricity units -2518 @11.007p per Kwh. Gas units - 6532.2@ 3.075p per Kwh Bill d) paid £905 CR by DD .Total charges £940.60 (nothing carried forward) Outstanding balance £35.60 .Electricity units 3901 @ 11.007p per Kwh.Gas 10751.6 Kwh @3.075p per Kwh Bill e) paid £1010.60 CR by DD.Total charges £1092.99(nothing carried forward).Outstanding balance £82.39. Electricity units 3945.9 @11.07 per Kwh.Electricity units 391.1 @ 9.37p per Kwh.Gas units 11242.5 Kwh @ 3.075p per Kwh.Gas units 1719Kwh @ 3.09p per Kwh As you can see with that last bill there are two lots of gas and two of electricity .One pair is meant to cover the period extending between 28/01/2015 - 31/01/2016 and the other a period between 01/02/2016 -01/03/2016 when I changed my supplier I added the two columns .What they show is that I paid them £3381.60 and the billed me total of £3233.23.Both those figures must be wrong as there is no way I paid them that amount.

I was with EE for a relatively short period before I went to another company - GB energy who have subsequently gone bust. The thing that struck with EE was that their bills never made any sense to me. From a period covering 28/01/2015 to 25/01/2016, I received 4 bills: Bill a) covering period between 28/01/2015 -10/04/2015 shown I was in debit by -£30.32 ( received on 11/05/2015) Bill b) covering period between 28/01/2015 -05/10/2015 shown I was in credit by £171.189 ( received on 07/01/2016) Bill c) covering period between 28/01/2015- 05/10/2015 shown I was in credit by £95.81 ( received on 07/01/2016) Bill d) covering period between 28/01/2015 -01/03/2015 shown I was in debit by £35.60( received on 27/012016 Then on 20/09/2016 when was with another provider, I got another bill for 28/01/2015 -01/03/2015 showing I was in debt by £82.39 which I paid hoping that would be the end of it unfortunately I have been getting a number of phone calls from Credit Style which I have not responded to Today when I rang back a number that was with an email they sent me . No one replied but there was a recorded message to which I replied I had no idea what all these phone calls were about and left it at that. I really don't know what to do about this and would welcome some advice. Thanks