Workers at an Amazon warehouse in Britain will walk out for seven further days in an escalation of a dispute over pay, their trade union said on Monday.

Last month GMB union members at the warehouse in Coventry, central England, staged the first ever strike at the U.S. e-commerce giant’s operations in Britain.

GMB said more than 350 staff at Coventry warehouse would now take further industrial action on Feb. 28, March 2 and March 13-17.

“Amazon bosses can stop this industrial action by doing the right thing and negotiating a proper pay rise with workers,” GMB Senior Organiser Amanda Gearing said in the statement.

Amazon, which employs 75,000 people across the UK, did not immediately respond to Reuters’ request for a comment.

It has previously said it already offers competitive pay and comprehensive benefits.

The company increased starting pay by 50 pence to a minimum of between 10.50 and 11.45 pounds per hour last year, compared with a government mandated National Living Wage which will rise to 10.42 pounds an hour from April.

GMB has said the Amazon Coventry workers are demanding 15 pounds an hour, to help cope with surging inflation and a cost-of-living crisis which has sparked strikes across a range of different sectors in Britain over the last few months.