Consumer advocacy groups are calling on the Department of Transportation to crack down on dealerships offering questionable sales terms to customers participating in the government’s Cash for Clunkers program.

The groups complained that some dealerships have pressured customers to sign agreements forcing them to repay their Clunkers rebate if the dealership isn’t reimbursed for the sale. The DOT says car buyers are not required to sign the so-called contingency forms to qualify for a Clunkers transaction, but the groups said the waiver should be banned altogether.