Bad debit order dates

Since I signed a cellphone contract with mnt things are not going as per our agreement they debit at any day of the month while our agreement is on 27 on the month. Always they put extra changes. Pls try to debit on 27 not later than that with no extra charges. We also agreed with 1 gig for day but now the separated to 500 day and 500 night. Pls I do not want to publish my concern to other media platforms.