They watch Indian serials in Hindi and Bengali channels. Star Jalsha and Star Plus are the most popular channels in BD.
BD channels hardly show any entertaining shows. All channels show news and political talk shows. So viewers who seek entertainment have no other options than Indian channels.
Recently a new BD channel Deepto TV showing a Turkish TV serial in Bengali which is very popular but Bangladeshi Bengali shows don't cater the attention of viewers hence the craze for Indian Bengali and Hindi serials.
To counter that Bengali dubbed Turkish serial instead of making a good Bengali serial another channel is showing a very old Indian Hindi serial Tipu Sultan in Bengali which was earlier shown in state owned BTV in 90's.
You can say Bangladeshis pretty much depend on Indian channels for entertainment.