On January the 13th I accepted a job offer telling me my start date, how much I'll get paid weekly and who my boss would be. A lady then called me to confirm all of this. She called me again on the 18th telling me my job title would be switched but I would still get paid the same. I printed out my offer letter and was sent a newer accepted letter with an edit. The only difference is I would get paid $10 less per week nothing bad about it. I started my job on Monday of January 23rd. Now it's the 26th the company I work for merged with another company. The main company that offered me the job bought the other company. I hope that makes sense. So after working a few days for the merged company I was told that I would get paid bi weekly now the other company that I was supposed to work for got paid weekly. On top of that the trainer who I talked to in secret told me I was getting over paid per hour and that I shouldn't tell anyone because the other workers weren't getting paid the same. I showed him my offer letter and he was like "wow I've never seen this before." But he was in the company that got bought and right now they are still transitioning. I accepted this job because of the pay and all. I won't find out how much I get paid till my pay check comes in. Is there anything legal I can do about this? I really want to keep what they offered and gave me.
You should be paid according to the terms of the offer letter you signed. If they don't, it's a clear breach of contract.
If they want to change the terms, in any way that has a financial impact (amount paid, when it's paid, etc), they need to give you a new offer and you need to sign it before it can take effect. If you don't, they can either stick to the old terms, or terminate you. (And you may have a case for unfair dismissal if the new terms are clearly worse, but if it comes to that, it's something you should take up with an employment lawyer.)