Need help to find Federal Law on the deletion of the PMI

I talked to a country wide rep yesterday about if I put 10% down for a non owner occupied property and I pay PMI now. When would the PMI be deleted? He told me once the loan to value reaches 80%, then PMI can be deleted. In fact every loan officer from different company told me the same thing. I told him the letter I received from country the day before yesterday stated clearly that the LTV need fail below 70% to delete the PMI, he told me he was trained with 80% and never heard of 70% and if the 70% is true then they should be told.
It appears to me that all the mortgage officers sell the mortgage to customer with 80% LTV information, but once you pay 10% down and PMI to get the loan you would have to make the LTV to 70% or 65% to be able to delete the PMI. The PMI you pay will be about 10% of the property value if you don’t make extra payment on a 30 year fixed mortgage. If the mortgage officer told me that I need bring the LTV below 70% to delete PMI instead of 80% I might do it differently. Because of the misleading information I am the one lost the money and mortgage are the one make the profit. I think that the mortgage officers are trained with wrong information to mislead customer.
Did anybody buy a 1-4 units investment property with 10% down 30 year fixed mortgage? If so, then what happened to you PMI?
I try to find the federal law on the deletion of the PMI on 1-4 units investment unit, any help would be appreciated.