i hope you changed with brand new tires, which brand? sometimes selected new tires are smuggled ones with old manufacturing dates/ tempered dates, in that case the tires could be bent already, in such case it is advisable to switch with fresh tires imported legally with local warranty. also Chinese brand low cost tires can also have some quality issues.
if you have changed with 2nd hand tires, and even after multiple alignment attempts if problem is not getting resolved, then its problem with tires not with your car.
Chinese alloy rims are also notorious but mostly they have wheel balancing issues which occur at high speeds.
PS: i hope wheel balancing was also done along with alignment.